THE 
OSTEOLOGY' OF THE COLYMBUS TORQUATOS; 
WITH NOTES ON ITS MYOLOGY. 
BT ELLIOTT CODES, A.M., M.D. 
Head September 16th, 1863. 
The Natatores Brachypteri, or Urimtores, so restricted as to exclude the Penguins, (Ptilopteri,) 
form an exceedingly natural group, quite closely adhering to a peculiar type of structure, 
as regards their bony framework and the muscles which act upon it. Their essential char- 
acteristics are found in the possession of a structure which, while it secures quite vigorous 
powers of flight, yet attains to by far its most perfect development in the production of 
natatorial powers, (unequalled except by those of the Penguins,) at a great sacrifice of capa- 
bilities for terrestrial locomotion. Progression on land is generally slow, awkward, and con- 
strained ; and is seldom or never protracted to any considerable distance, the bird always 
remaining in close proximity to the water. On the other hand, progression on or through 
the water is accomplished with a degree of facility and energy which at once stamps a 
peculiar character upon the whole tribe. 
These remarks apply with particular force to that family of birds of which the common 
Loon may be considered as typical. In the genus Coly mbits, the peculiarities of structure 
above alluded to reach their maximum of development, for the production of unsurpassed 
natatorial powers, at the expense of capabilities for terrestrial locomotion, which latter 
are remarkably imperfect. Both the osseous and the muscular system, therefore, of Co- 
lymbus torqmtus, are probably typical of the morphology of these systems throughout the 
Urimtores, and are thus specially interesting and instructive as exemplifying the natatorial 
type of structure in a very perfect manner. The descriptive anatomy of them is applicable 
in a greater or less degree to the other genera of the tribe. The Podicipidce are of course 
the most intimately allied • some of the genera of the Alcidce may be more aberrant. 
Although peculiarities are found in the whole structure of the bird, yet they of course 
are most marked in the posterior extremities; and I have therefore, in my descriptions, 
entered specially into detail regarding these parts, passing over other portions in a more 
summary manner. In the following pages, so far as the bones are concerned, it has been 
attempted to present the descriptive anatomy of the entire skeleton; while in the account 
of the muscles, only the more important have been noticed, special attention having 
been paid to those of the posterior extremities. In a paper like the present, it seemed 132 
COUES ON THE OSTEOLOGY 
impossible to present a complete myology, while such a procedure would be of doubtful 
utility. The scope of the paper is perhaps expressed in its title. Whatever may be its 
deficiencies or inaccuracies, it is offered in the hope that it may contribute its mite to the 
sum total of our knowledge of the anatomy of the class. 
Of the Shill 
In the adult skull, the various bones of the cranium are, with the exception of course 
of the pterygoid and the tympanic elements of the temporal, so completely anchylosed that 
even the traces of their original sutures are scarcely discernible. The same may be said 
of the majority of the facial bones, especially the nasal, intermaxillary, and superior max- 
illary. The fronto-maxillary “ articulation,” however, and the palato-pterygoid and tympano- 
malar, remain freely movable. I will first notice the individual bones of the head, as well 
those which are anchylosed as those which remain permanently separated, and afterwards 
examine the skull, as a whole, upon its several aspects. 
The occipital forms the posterior, and a small part of the inferior, aspect of the skull. Its 
basilar process is nearly smooth and flat, somewhat of a diamond shape, bounded anteriorly 
by the occipito-sphenoidal anchylosis, more laterally by the petrous portion of the temporal, 
posteriorly by the atloid condyle and foramen magnum. Just anterior to the condyle 
there are two considerable depressions for ligamentous attachments; and just externally to 
these, two slight elevations. Laterally, the occipital spreads out and rises into two promi- 
nent processes, the apices of which are rough for the attachment of muscles. From these con- 
dyles and from the basilar process, the “ spinous ” element of the bone arches upwards toward 
the parietal, leaving inferiorly the large orifice, the foramen magnum. On either side 
these “spinous” plates are much depressed and rough for the attachment of muscles, 
and are separated from the parietal bones by elevated curved crests. On the median 
line they rise up to form an arched longitudinal elevation. The foramen magnum is broadly 
oval in shape, its long axis being antero-posterior. Above, its margins are very thin, being 
formed by the thin “ spinous ” plates of the occipital; they become laterally considerably 
thicker. Inferiorly, the edge of the foramen is occupied by the single condyle forming the 
occipito-atloid articulation. Its face is exceedingly convex; its general outline a semilune, 
the cornua presenting upwards, the greatest convexity directly downwards. Around the 
foramen magnum are several other foramina, for the transmission of some of the cranial 
nerves. 
Sphenoid. The basilar process of this bone projects directly forwards from the basilar pro- 
cess of the occipital, in the median line, having on either side the pterygoid and palate 
bones, from both of which it is entirely separated. In this species, in which the orbits are so 
defective as to their bony parietes, it forms nothing of the floor of the orbits, but, by a vertical 
lamella of bone which projects forward, it contributes to form the inferior portion of the 
very deficient septum which exists between the orbits. From the posterior part of the base 
of the bone, the two “ orbital ” processes or plates extend upwards, forwards, and outwards, 
as thin lamellae. They form the posterior walls of the orbits, separating them from the 
cranial cavity. Each is pierced near the median line, at its lower border, by the very large 
subcircular optic foramen; and external to these, by a smaller opening for the ophthalmic 
division of the fifth nerve. The second and third divisions of the fifth together perforate 
the bone much further back and more externally, in the depression just above the body OF COLYMBUS TORQUATUS. 
133 
of the tympanic bone. Just above the optic foramina are two others of considerable 
size, and of a regular quadrilateral shape. The alae majores form that part of the skull 
intermediate between the zygomatic portion of the temporal and posterior orbital pro- 
cesses of the frontal. 
Parietal The complete anchylosis of the roof of the cranium leaves no traces of the 
original margins of these bones. The space which represents them is bounded posteriorly by 
the elevated crest marking the edge of the occipital, below and behind by the temporal, 
below more anteriorly by the alae majores; on the roof of the skull they may be con- 
sidered as projecting about as far forward as a line drawn between the two posterior orbital 
processes of the frontal. The space thus included is for a little distance on the anterior 
portion smooth, and covered only by the skin; but by far the greater portion of the bones 
form on either side rough, irregular, greatly depressed fossae, generally styled the “ temporal 
fossae.” These are entirely filled up, in the recent state, to the level of the rest of the skull by 
the temporal and masseter muscles. The two fossae are separated from each other by a wrell- 
marked median longitudinal crest, from the anterior extremity of which two other equally 
elevated ridges proceed on either side to the posterior orbital processes, and form the 
anterior boundaries of the fossae. 
Temporal. This bone forms the infero-posterior angle of the skull, being situate between 
the parietal, occipital, and sphenoid. Superiorly, the “ squamous ” portion sends forward 
and downward the zygomatic process. The mastoid process seems to be indicated in that 
part of the bone which is continuous with the condyloid process of the occipital; it gives 
origin to the analogue of our digastricus. The petrous portion of the bone containing the 
osseous elements of the organ of hearing, lies internally on the inferior aspect of the skull, 
anchylosed with the side of the occipital basilar process. To the under surface of the 
zygomatic process is articulated the movable element of the temporal. 
Os pedicellatwn. This, the tympanic element of the temporal bone, articulates, by two 
separate, oval, very convex facets, placed side by side in a line oblique to the axis of the 
body, with two corresponding deeply concave depressions at the bottom of the fossa on the 
under surface of the zygomatic process. The depth of the depression in which the head of 
the pedicellate bone is received, together with a projecting border from the edge of the 
zygomatic process, tends to make the joint a very strong one. 
From this articulating head the bone projects directly downwards and a little forwards 
for about three fourths of an inch. It first sends off its orbital process, a stout compressed 
process of bone, projecting directly forwards and upwards into the orbit. This process has 
a considerable upward curve; its superior margin being concave, and running up quite to 
the head of the main bone; its inferior margin is convex, and merges into the main bone 
a little above the temporo-maxillary articulation. The top of this process is rough, for 
muscular attachments. 
After giving off this orbital process, the bone becomes a little constricted into a “ neck,” 
upon which is supported the broad, irregularly shaped, and uneven head for articulation 
severally with the pterygoid, malar, and inferior maxillary. 
The pterygoid facet is placed on the side of the head of the bone, just internal to, and 
below, the root of the orbital process. It is a single, obliquely elongated, smooth, very 
convex tubercle pointing inwards and forwards, on which the concave head of the pterygoid 
bone is placed. It presents something of the characters of the ball-and-socket joint, 
although rotation in all directions is not equally perfect. 134 
COUES ON THE OSTEOLOGY 
Upon the opposite, i. e., the outer aspect of the head of the pedicellatum, is placed the 
concavity for the reception of the head of the malar bone. It is on a lower level than the 
pterygoid facet, and presents more directly forwards. It is a nearly circular and exceed- 
ingly deep cavity. The small globular head of the malar is received into its concavity. 
The somewhat extensive surface resulting from the expanded head of the bone is wholly 
occupied by the facet for the inferior maxillary. It is of an exceedingly irregular shape 
and uneven surface; in general terms, it may be said to be laterally much wider than long; 
to have a central depression bounded on each side and behind by elevations; and to be 
nearly divided into two lateral halves (corresponding to the lateral development of the 
head to produce the pterygoid and malar articulations), by a notch which cuts deeply into 
the posterior edge of the articulating surface To the inequalities of this surface, depres- 
sions and elevations in the lower jaw are accurately coaptated. 
It is by this movable element of the temporal bone that the superior mandible receives 
the slight motion which it is capable of. The movements of this bone are transmitted by 
the malar to the superior maxillary, and by the pterygoid to the palatine, and thus the 
upper jaw is elevated or depressed according as the pedicellate moves forwards or back- 
wards. The extent of motion that the upper jaw is capable of, however, does not seem to 
be as great as is the case with many other families. 
Pterygoid. These are two straight slender bones about three fourths of an inch long, 
running obliquely inwards and forwards from the pterygoid facet on the inner edge of the 
head of the pedicellatum, to the posterior extremity of the palatine, with both of which 
they are movably articulated. Their shafts are slender, triangular on a transverse section, 
marked on their superior faces with a longitudinal groove. Both extremities expand into 
articulating facets. That of the posterior end is the largest; and besides the oval concave 
facet already noticed, by which it articulates with the pedicellatum, there is externally a 
small irregular projection which abuts against the inner side of the root of the orbital pro- 
cess of the tympanic bone. This seems to considerably restrict the extensive motion 
which ordinarily results from a ball-and-socket joint, and to give it rather the character of 
a free ginglymus. 
The pterygo-palatine joint is a peculiar one. Two uclaws,” so to speak, project respec- 
tively from the upper and under surface of the bone, and grasp between them a small pro- 
jecting point of the extremity of the palatine. The resulting articulation is most admirably 
adapted to its functions; chiefly that of pushing the palatine bones directly forward, but 
allowing also some inconsiderable lateral motion. 
Frontal. This bone forms the whole of the roof of the orbits, but only a comparatively 
small part of the parietes of the cranial cavity proper. Its anterior border is quite straight, 
forming the directly transverse fronto-maxillary “ articulation.” The lateral margins are at 
first slightly bulging and convex, forming the anterior orbital processes; are then ascending 
and deeply concave, forming the superior margin of the orbits; and finally the bone 
stretches far downwards and backwards, to form the pointed prominent overhanging poste- 
rior orbital processes. Its posterior border is on the roof of the cranium anchylosed with 
the parietal, so as to leave no trace of the original suture; and in the back part of the 
orbits is equally fused with the orbital processes and alee majores of the sphenoid. 
Its superior surface is at first thick and rapidly ascending, forming the prominence of 
the forehead; in the rest of its extent it is flat, and gradually rises as it runs backward. It 
is marked in its whole length with a deep semilunar depression on each side, the con- OF COLYMBUS TORQUATUS. 
135 
cavity of which is parallel with and corresponds to the concavity of the superior margin of 
the orbit; the convexities of the two meet on the median line, where they are separated 
by a longitudinal ridge. The bottoms of these semilunar grooves are pierced with nu- 
merous minute foramina. At the anterior extremity of each is a large oval foramen, 
which transmits to the mucous membrane of the nasal passages the duct of the “ nasal ” 
glands which lie in these depressions; the secretion of which moistens and lubricates 
the pituitary membrane. Posteriorly, on the superior surface of the frontal, there is 
formed by the divergence of these two nasal fossae, and by the crests which form the 
anterior boundary of the parietal fossae, a smooth, diamond-shaped, elevated tablet of 
bone, almost the only part of the surface of the skull over which the skin is directly 
superimposed. 
The chief noticeable feature on the under surface of the bone is the continuation for- 
ward of the osseous canal through which the olfactory nerves escape from the cranium, as 
deep well-marked canal, spreading out anteriorly into a still deeper and larger oval fossa. 
This fossa occupies part of the frontal bone, but still more of the ethmoid; external to the 
fossa is the foramen opening into the beds for the nasal glands, ';h a groove running from 
the anterior edge of the foramen into the nasal passages, just along the inside of the root 
of the lachrymal bone. 
Ethmoid. This is little more than a thin vertical lamina, placed in the median line, its 
superior margin anchylosed with the inferior surface of the frontal; its inferior margin sim- 
ilarly united with the long, projecting, basilar process of the sphenoid; its sides forming 
anteriorly what there is of an imperfect inter-orbital septum. Its posterior edge is thin 
and sharp, and forms the anterior margin of the large circular opening between the orbits. 
Its anterior margin spreads out superiorly so as to become of considerable width where it is 
fused with the frontal; below it is deeply concave, running forward some distance, with a 
pointed extremity. The superior part of the lateral surface of the ethmoid is hollowed 
into a shallow fossa for the olfactory nerve, as already mentioned. There is nothing to cor- 
respond with our cribriform lamella, nor with the spongy convolutions of the lamellae 
of bone which so preeminently characterize this bone in mammalia. It still, however, per- 
forms the ordinary functions of separating the orbits from each other, and the nasal from 
the ophthalmic cavities, and of supporting the ramifications of the olfactory nerves. 
Bones of the Face. 
The facial bones, like the majority of the cranial, are in adult life anchylosed more 
or less completely with each other; the complex osseous structure thus formed having, as a 
unit, slight motion with the cranial bones, by means of the fronto-maxillary, pterygo-pala- 
tine, and tympano-malar articulations. Owing, however, to their peculiar form, the precise 
line of anchylosis can in most cases be more readily detected than in the bones forming the 
cranium. All the bones of the human face are repeated, with, it is true, exceedingly diverse 
shapes, but yet so markedly as to give rise to no difficulty in homologizing them; but 
the intermaxillary bone, although fused with the suprarnaxillary as in man, in birds forms the 
most prominent and important element of all, preponderating vastly over the superior 
maxillary proper. 
Lachrymal. From its position and connections this bone would seem rather to apper- 
tain to the cranial than the facial group. It is a thick, stout process of bone, five eighths of 136 
COUES ON THE OSTEOLOGY 
an inch long, projecting downwards and backwards from the under surface of the anterior 
corner of the frontal. It forms the continuation of the anterior boundary of the orbit. It 
projects downwards till it almost touches the malar bone, but is, however, quite uncon- 
nected with this or any other bone of the face, and does not have the least motion with them, 
being firmly anchylosed to the frontal. Besides forming the anterior continuation of the 
orbit, it forms a very partial and defective outer wall to the posterior part of the nasal 
passages. This bone, indeed, and the descending ramus of the nasal, are the only osseous 
lateral boundaries of the nasal passages throughout their whole extent. 
Nasal. Firmly anchylosed basally with the root of the nasal process of the intermax- 
illary ; movably articulated with the anterior border of the frontal. While its borders 
cannot be accurately defined, in consequence of its complete fusion with the intermax- 
illary, it sends downwards and forwards, at an acute angle, a conspicuous, stout, laterally 
compressed process which anchyloses with the superior maxillary, appearing to be a 
direct continuation downwards of the intermaxillary. This process forms the posterior wall 
of the osseous boundary of the aperture of the external nares; forms with the lachrymal 
the lateral osseous boundary of the nasal passages; and connects the base of the nasal pro- 
cess of the intermaxillary with the superior maxillary bone. 
Intermaxillary. This is by far the most important, as it is the largest and most con- 
spicuous bone of the face; its various modifications in different families and orders of birds 
affording much the same data for zoological classification as do the teeth of the mammalia. 
In this species it measures three and a quarter inches in total length. Its outline along the 
culmen is slightly convex, especially terminally; both the mandibular and lateral outlines 
are a little concave. Distally, the bone consists of one piece, which is acutely pointed, 
arched superiorly, inferiorly with a deep longitudinal excavation, the beginning of the palate. 
About one and a half inches from the top it divides into three processes: a superior, mesial, 
« nasal ” process, much the largest, running backwards as an elevated ridge supporting the 
culmen of the bill, anchylosed basally with the nasal bones and movably articulated with 
the frontal; and two lateral, basal, “ mandibular ” processes running along and forming the 
continuation of the tomia of the upper mandible, and finally merging by anchylosis into 
the superior maxillary, a little anterior to the zygomatic anchylosis. 
The recess formed laterally by the divergence of the nasal and mandibular processes 
forms, with the nasal process of the nasal bone posteriorly, the large osseous boundary of 
the aperture of the external nares. It is an inch and a quarter in length, by a third of an 
inch high, sub-oval in shape, being narrow and compressed anteriorly. 
The divergence of the mandibular processes leaves on the palate a narrow longitudinal 
opening, one fourth of an inch broad, covered with the lining membrane of the palate, 
except at the posterior part where begins the opening of the posterior nares. The fissure 
then becomes cleft in two by the vertically projecting vomer. 
Superior maxillary. This bone is of inconsiderable size. It is difficult to define its con- 
tour with precision, as anteriorly it merges insensibly into the mandibular process of the 
intermaxillary; internally it is anchylosed with the palatine; superiorly the nasal bone 
becomes fused with it; while posteriorly it seems prolonged indefinitely into the long malar. 
That part of it which chiefly maintains its separate identity consists of a horizontal plate 
projecting directly inwards from the back and inner side of the bone towards the median 
line of the skull. This plate stretches to within a tenth of an inch of its fellow, the 
two being separated by the vomer, which passes between them. This represents the OF COLYMBUS TORQUATUS 
137 
palatal process. From its inner border all around there arises a thin, delicate, concavo- 
convex lamella of bone, projecting upwards, outwards, and backwards, its free rounded 
margin inflected downwards so as to partially occlude a quite deep fossa, probably the 
analogue of our maxillary sinus, antrum Highmorianum. While the bones forming this 
sinus are tolerably broad, so as to divide the long palatine fissure into an anterior and pos- 
terior part, they are so depressed vertically as scarcely to rise at all into the large nasal pas- 
sages. But for the fact that it forms this quite conspicuous “ antrum,” the superior maxillary 
would seem to constitute little more than an osseous band of connection between the four 
bones already mentioned as anchylosing with it. The important part which it plays in 
mammalia generally in the formation of the upper mandible is here quite usurped by the 
intermaxillary. 
Malar or “ zygomatic.” Long and slender, measuring about two inches in length. They 
form the lateral boundary of the inferior aspect of the skull. Arising from a perfect anchy- 
losis with the superior maxillary, they at first curve a little outwards; then more outwards, 
with an inclination downwards; finally curving rather abruptly inwards and slightly 
upwards to the outer edge of the head of the pedicellatum. They transmit the motion of 
the latter directly to the superior maxillary, as the pterygoid do to the palatine. 
The malar bone, properly speaking, extends only three fourths of the distance to the 
pedicellatum, the remaining being made up by the true zygomatic element of the tem- 
poral. Traces of the fusion of the two are still clearly traceable in several oblique lines 
and sulci. 
Palatine. The palate bones are long and slender, lying along each side of, and near to, 
the median line of the skull. The width of their separation from each other forms the 
palatal fissure. This amounts on an average to about a quarter of an inch; but at their 
posterior extremities the bones almost touch each other, being separated only by the width 
of the thin sphenoidal spine. They begin very near the anterior extremity of the superior 
maxillary bone, lying along its inner border, being more or less completely anchylosed 
with it, and extending to within half an inch of its posterior termination. Thus far they are 
simply plain, narrow, flattened spiculse of bone; but shortly after leaving the maxillary 
bones, they dilate laterally into very thin lameihe, their edges so much inflected downwards 
as to give a transversely concave outline to their inferior surfaces. This dilatation ends 
quite suddenly by a rounded free margin, which slopes inward and bends upward to form 
the little projections which are grasped by the ends of the pterygoid bones. 
From the anterior portion of the superior aspect of these horizontal plates there rises 
quite gradually a thin vertical lamella, which curls upon itself upwards and inwards towards 
the median line, forming that part of the inner edge of the bones to which the vomer is 
articulated. 
Vomer. The vomer, as usual, is situated directly in the median line, forming an incom- 
plete septum between the right and left nasal passages. It is just one and a half inches in 
length. Its inferior border, for one inch anteriorly, presents an exceedingly thin edge. For 
the rest of its length it is bifurcate, the right and left portions divaricating from each 
other at a very acute angle, to articulate with the corresponding palatines. They are 
probably, however, more or less completely anchylosed with the latter, so that little or no 
motion is allowed. The superior surface of the bone is deeply grooved longitudinally for 
nearly its whole extent; the edge of the vertical lamella, the conjoined sphenoid and eth- 
moid, being received into this groove, and riding freely through it during the movements COUES ON THE OSTEOLOGY 
138 
of the upper mandible. A little posterior to the termination of the ethmoidal spine, the bone 
sends out on each side a small but distinct lateral horizontal lamella. These run forward 
for half an inch, gradually narrowing till they no longer project; the groove along the 
superior surface of the bone also becomes obsolete; and the vomer continues a little way 
farther forwards, merely as a slender, very acute spine. 
Inferior maxillary. Several of the original elements of which this bone is composed 
remain, as usual among the natatores, only incompletely anchylosed in adult life. The 
symphyseal elements present the most complete anchylosis, being firmly united for a little 
more than an inch. The angular and supra-angular pieces are also completely consolidated. 
The union between the two condyloid elements is less perfect, there being still traceable 
the evidences of their line of consolidation. The splenial element, however, remains quite 
distinct from all the others, except just at its lower end, where it is united to the angular. 
The piece produced by the union of the angular and supra-angular remains quite separate 
from the symphyseal element, being joined with it by the usual gomphosis. Along the 
inside of this joint the splenial element is applied obliquely; and posterior to it is the 
ordinary large unossified space. On the outside of the mandible proceeding from the 
gomphosal suture is the long oval foramen leading into the bone; and on the inside, nearly 
similarly situated but lower down, is a shorter and broader one. 
In its general outline, this bone is quite straight, the rami not rising above the plane of 
the body of the bone, and the articular surface being on a level with its superior border. The 
tomal edge of the bone is almost perfectly straight, as far from the tip as the symphyseal 
element extends; then the superior border rises above the level of the articular facet, with 
an irregularly indented and somewhat curved outline; the principal elevation forming the 
“ coronoid ” process. This curved elevation terminates posteriorly in the depressed, broad, 
irregularly indented articular surface, the inequalities of which are accurately coaptated 
to those of the articular facet on the os pedicellatum. 
Posterior to the articulation, almost immediately continuous with it, is the well-defined 
triangular depression, presenting backwards and upwards, for the attachment of the prin- 
cipal depressor of the lower jaw, the so-called u digastricus.” This space is bounded by 
well-defined raised borders; its inferior angle forms the posterior extremity of the bone. 
The inferior edge of the bone is sinuate for its whole length. It is nearly straight from 
the tip as far as the consolidation of the symphyseal elements extends. Then, with a 
slight convexity, it curves upwards, and again downwards to the angle, forming an 
extensive concavity from the termination of the symphysis to the angle. The angle is 
pretty well marked though not acute, and it does not project much further below the 
level of the bone than the coronoid process does above it. From the angle, the inferior 
outline runs backwards with a moderate degree of upward obliquity, to just opposite the 
posterior border of the articulating surface, where it turns downwards with an abrupt con- 
cavity, to terminate at the apex of the triangular space above mentioned. 
In its general shape and structure, this bone is very strong. The symphyseal elements 
are quite thick as well as deep, and their union very firm. More posteriorly, the bone is 
thinner, but this is compensated for by its greater depth. The articulating surfaces are 
very strong; and the total want of an obliquity in the line of union of the rami with 
the body of the bone confers a shape upon it which insures great stability and firmness. 
Of the Cranium as a ivhole. Having considered the several individual pieces which go to 
make up the cranium, we will briefly notice the general characteristics of the skull as a OF COLYMBUS TOBQUATUS. 
139 
quadrilateral pyramid, of which the tip of the bill is the apex, the occipital bone chiefly 
the base, and the superior, inferior, and two lateral aspects respectively the four sides. 
The base presents rather a pentagonal outline. Superiorly, the two occipital crests con- 
verge at an angle on the median line, terminating below on each side with the mastoid 
processes. The lateral boundaries of the pentagon are formed by the pedicellate bones, 
the tempero-maxillary articulation, and the surface at the end of the inferior maxillary 
bone for the attachment of the digastricus. The fifth side of the pentagon is an imaginary line 
drawn from the posterior extremities of the rami of the lower jaw. Exactly in the centre 
of this pentagon is the semilunar condyle for the cranio-vertebral articulation; just above it 
is the large oval foramen magnum, between which and the occipital crests lies the flat, de- 
pressed “spinous” plate of the occipital, the two sides of which rise into a longitudinal 
ridge at their union along the median line. On either side, the mastoid processes project 
conspicuously. Beneath these, and between them and the ossa pedicellata, are situate the 
internal organs of hearing. The space around the foramen magnum is pierced by several 
foramina for the transmission of nerves. 
The superior aspect of the skull is bounded posteriorly by the occipital ridge, laterally 
by the parietal bones, the superior margins of the orbits, and the sides of the intermax- 
illary. The zygomatic processes of the temporals are the first lateral protuberances from 
behind forward; between these and the post-orbital processes, the crotaphyte depression is 
deep and well marked. The post-orbital processes are long and acute, the width between 
their apices representing the greatest lateral width of the skull. Anterior to these, the mar- 
gins of the superior aspect of the skull are deeply concave, by the indentation formed by the 
upper margins of the orbits; the ante-orbital processes form a slight concavity on each side, 
just posterior to the fronto-maxillary suture. The tapering intermaxillary bone forms the 
remainder of the boundary of this aspect of the skull; its superior surface is occupied, as 
far forward as the post-orbital processes, by the large, deep “ temporal ” fossa, formed chiefly, 
however, by the parietal bones. Along the margins of the orbits lie the two long semilunar 
depressions for the nasal glands, separated by a median ridge from each other, their divari- 
cation posteriorly leaving between them and the temporal fossae a central elevated, smooth, 
lozenge-shaped space. At their termination the glandular depressions are perforated 
with oblique oval foramina, which transmit their ducts through to the nasal cavities. The 
curved fronto-maxillary suture extends transversely across from side to side, its convex- 
ity presenting backward; the smooth nasal bones come next; and, taking its origin from be- 
tween them, and stretching from the frontal bone to the tip of the bill, is the intermaxillary. 
The inferior aspect is bounded laterally and apically by, and contained chiefly within, 
the two sides of the lowTer jaw, which divaricate from the symphysis, and extend the 
whole length of this aspect of the skull. Posteriorly, on the median line, lies the basilar 
portion of the occipital • just anterior to it, the spheno-occipital anchylosis, from which runs 
forward in the median line the elongated vertical spine of the sphenoid, to be received into 
the cleft of the vomer, and there anchylosed with the ethmoid. On either side of this spine 
are the pterygoid bones, running backward from the pterygo-palatal articulation, and diverg- 
ing outwards to join the head of the pedicellate bones. More anteriorly, the flat, elongated 
palate bones extend the whole distance from the pterygoid to the bases of the superior 
maxillary, lying on either side of the median line, the vomer being interposed between 
them and articulated with them by its posterior bifurcated extremity. As far as the an- 
terior extremity of the vomer, the spaces leading up into the orbits and nasal passages 140 
COUES ON THE OSTEOLOGY 
have been divided along the median line into a right and left; but beyond this the palatal 
fissure is not cleft, but a single broad opening leads into the nares. The anterior single, 
and posterior double fissures are, however, continuous with each other, as the superior max- 
illary does not extend far enough inwards to meet the vomer. 
The lateral aspects are each of a subtriangular shape, bounded by the margins of the 
three surfaces just described, with the planes of which they are united nearly at right an- 
gles. Their union with the posterior aspect is, however, at less than a right angle, in con- 
sequence of the lateral tapering of the skull from base to tip. Posteriorly the mastoid 
and zygomatic processes form conspicuous projections, below and internal to which are 
the internal organs of hearing. Anterior to this, extending between the under surface of 
the zygoma and the inferior maxillary articulation, is the pedicellatum, sending upward 
and forward into the orbit its orbital process. Just above the root of this process is the 
large circular foramen leading into the cranium, which transmits the second and third 
divisions of the fifth nerve; and the pterygoid bones are seen starting from just inter- 
nal to the root of the orbital process, and running inward to the palatal. 
The orbits occupy by far the largest portion of this lateral aspect of the skull. As usual 
among the Natatores they are exceedingly defective, not only as to bony margins, but as 
to septa between the two, and between them and the nasal and pharyngeal passages. The 
roof is formed centrally by the slight expansion of the frontal bone; the strongly de- 
veloped post-orbital processes make a more complete arch posteriorly; while anteriorly, 
the slightly developed ante-orbital processes are eked out by the large strong lachrymal 
bones, which project downwards and backwards from the frontal quite to the malar, and 
complete the margin anteriorly. A very imperfect floor for the orbits is afforded by the 
slender elongated malar, the superior border of the inferior maxillary just within the 
malar, and by the horizontal expansions of the palatal. But the orbit is most defective 
posteriorly, where a bony parietis is quite wanting, and its place supplied by the temporal, 
masseter, and pterygoid muscles. The septum between the two orbits is formed by the 
vertical lamina of the sphenoid and ethmoid, but is very defective, a large circular aperture, 
more than half an inch in diameter, being closed only by dense membrane. Just at the 
posterior edge of this septum are seen the very large foramina for the optic nerves. 
There is really only one foramen leading into the cranium; but this is divided into two by 
the posterior edge of the vertical sphenoidal lamina, so that the nerves enter the two 
orbits by separate orifices. Other foramina, for the transmission of nerves and vessels, are 
found immediately about the optic. On the roof of the orbit is seen the longitudinal 
groove, emerging from the bony canal which transmits the olfactory nerve; and anterior 
and external to it, the large oval aperture which gives passage to the duct of the nasal 
gland. There is no bony septum between the orbits and the nasal passages. 
Just anterior to the orbits, and separated from them by the lachrymal bone, is a trian- 
gular space. It opens into the orbits and the nasal passage, and communicates directly 
with its fellow, and projecting up in it is seen the horizontal incurved lamella of the 
superior maxillary. It is bounded below by the fused malar and superior maxillary 
bones, posteriorly by the lachrymal, anteriorly by the descending process of the nasal. 
This separates it from a large suboval aperture between the mesial and lateral rami of the 
intermaxillary, which forms the osseous margin of the external nostrils. It is one and a 
fourth inches long, by one fourth broad. Its axis is parallel with the nasal process of the 
intermaxillary, and therefore somewhat oblique to the longitudinal axis of the whole skull. OF COLYMBUS TORQUATUS. 
141 
This aperture communicates directly with its fellow, and also with the palatal fissure, as 
as well as with the nasal passages generally. 
Of the Vertebral Column. 
Cervical vertebrae. The cervical portion of the spinal column consists of thirteen vertebrae. 
These, as usual among Aves, are very freely movable upon each other, not only antero- 
posteriorly in the direction of the axis of the body, but the lateral movement is also 
exceedingly free. There does not appear, however, to be anything very peculiar in their 
articulations with each other. The vertically concave and horizontally convex facet 
upon the posterior extremity of one vertebra is received into the vertically convex and 
horizontally concave anterior extremity of the next succeeding ; and the smooth flat facets 
upon the oblique processes glide in the ordinary way upon each other. The planes of 
these articulations are so arranged as to produce, taken together, the ordinary “ sigmoid ” 
flexure of the neck of the bird. The feature of the extensive lateral motion of the 
neck appears to be more strongly marked than is ordinarily the case among the Urinatores, 
except perhaps the Podicipidae; the long-necked genera of which, such as JEchmophorus, 
etc., probably surpass it in this respect. This lateral motion is most extensive between the 
lower cervical vertebras. 
Although these vertebras possess characters which most readily separate them from those 
of any other portion of the column, they yet differ greatly from each other, in different 
portions of the neck. Throwing out of consideration the atlas and axis, which of course 
are quite unlike the others, we still find that scarcely any two vertebrae possess exactly 
the same shape, size, and special characters. Beginning with the third vertebra, and pro- 
ceeding backwards, we find that the length of the bodies increases successively to about 
the eighth or ninth, when it again decreases rapidly, so that the last one is not so long as 
the third. The body of the third is thin, being exceedingly compressed vertically; and 
coincidently with the lengthening of each one successively to the eighth or ninth, they 
grow wider, and comparatively not so deep vertically; those that follow, however, do not 
again grow more compressed as they shorten; but on the contrary become broader and 
broader, so that the last one is as wide as deep, and very stout and strong. With this 
widening, there is also, towards the posterior extremity of this portion of the spine, a very 
high development of the transverse processes of the anterior extremities of each vertebra. 
This is so considerable, that the width across these transverse processes much exceeds the 
length of the whole vertebra. These processes are also exceedingly stout, with several 
roughened eminences for muscular attachments; and the foramen for the vertebral artery, 
which their two roots form, is as large as the spinal canal itself. Now as we proceed up 
the neck to the head, these transverse processes project less and less from the bodies 
of the vertebrae, and become less robust and angular, at the same time that they are 
antero-posteriorly elongated; and possess regular lamelloid walls, so as to form rather 
canals than simple foramina for the artery. 
The “ styliform processes ” or u rudimentary ribs ” appear to arise from the posterior 
aspects of the summits of each of the transverse processes, beginning with the third ver- 
tebra. They are directed backwards, exactly parallel with the axis of the column, and 
according to their length, form a more or less complete osseous covering and protection to 
the vertebral artery during its passage between any two contiguous foramina. These 142 
COUES ON THE OSTEOLOGY 
styliform processes on the third vertebra reach quite to the transverse processes of the next 
succeeding, and, by keeping pace with the lengthening of the vertebras themselves, are 
longest absolutely on the eighth and ninth vertebras. They now, however, rapidly shorten, 
and lose their very peculiar features, until on the last cervical vertebra they are merely 
little pointed projections from the posterior aspect of the transverse processes. This fact 
of their rapid absorption towards the thorax renders the determination of the first true 
dorsal rib perfectly easy. These styliform processes are firmly anchylosed with the 
transverse processes and bodies of the vertebra to which they appertain, but have no 
connection, other than ligamentous, with the next succeeding one. 
The superior spinous processes are well developed on the anterior vertebras, as promi- 
nent crests or keels, running the whole length of the surfaces of the bodies; so much 
laterally compressed as to be thin laminae of bone rather than “spinous processes.” 
Their shape on the third and fourth vertebrae is not unlike that of the keel of the sternum. 
They gradually decrease in size as they proceed backwards; until, on the ninth and tenth 
vertebrae, they amount to little more than slight compressed tubercles. These enlarge 
again on the eleventh and twelfth, and on the thirteenth have assumed the general 
features of those on the dorsal vertebrae. Between the dorsal surfaces of any two con- 
tiguous vertebrae there is the ordinary aperture, closed only ligamentously, leading into 
the spinal canal. 
The inferior spinous processes have the same general characters as the superior, i e., 
they are found well developed at both extremities of the neck, but disappear in the central 
portion. Thus the third vertebra has a very large, well-developed process, whose base 
occupies the whole length of the body of the vertebra. This is much smaller on the 
fourth, is scarcely appreciable on the fifth, and is totally wanting on the successive ones 
to the eleventh. On this one, however, a spinous process reappears abruptly, being 
larger than any of the anterior ones, and is especially noticeable for its great pro- 
jection forwards and downwards, and its exceeding thinness. The twelfth and thirteenth 
processes are successively smaller than this, but partake of all its general characters of 
shape. 
The axis is chiefly noticeable for the great development of its ventral and dorsal spines, 
the former of which extends far downwards as a thin compressed lamella of bone, larger 
than the ventral spine of any vertebra except the eleventh. Nearly all of the body of 
the vertebra seems to be really comprised in this spine; and the facet for the articulation 
of the body of the third vertebra is situate on its posterior edge just at its base. The 
roof of the spinal canal is quite flat, and from its median line rises the dorsal spinous 
process, not really so large as the ventral, but still quite stout and prominent, and 
terminating in a thickened tuberculous apex. The flat roof of the spinal canal spreads 
out posteriorly into the transverse processes, which bear their articulating facets directly 
upon their under surface. The oblique processes, for articulation with the atlas, have their 
facets presenting directly outwards; and these are received within the ring of the atlas. 
The large facet which articulates with the body of the atlas is regularly oval, and quite 
deeply concave; the odontoid process well developed, convex in every direction upon its 
articulating aspects, flat on the side which presents toward the spinal canal. 
The ring of the atlas is large, suboval in shape, its long diameter transverse. Pos- 
teriorly, it sends down on either side its slight transverse process, which overlies the 
anterior extremity of the axis. The fossa for the reception of the single occipital condyle OF COLYMBUS TORQUATUS. 
143 
is semilunar in shape, and very deep. Its concave inner border is formed to a considerable 
extent by ligaments, which separate it from the depression in which lodges the odontoid 
process of the axis, and serve to increase the depth of both these depressions. The body 
of the bone is, on the ventral aspect, prolonged as a spine of inconsiderable size, the 
commencement of the ventral series of processes. 
Dorsal vertebrae. If we consider the dorsal vertebrae as corresponding in number with 
the ribs, we should assign ten to this portion of the spinal column. The last three ribs, how- 
ever, correspond to vertebrae which are completely anchylosed to the sacrum as well as to 
the iliac bones, and at the same time they differ in several respects from the dorsal ribs 
proper. It seems more natural, therefore, to consider these ribs as really appertaining to 
the sacrum, leaving seven to be viewed as true dorsal ribs, and consequently to con- 
sider the number of dorsal vertebras to be the same. 
The transverse processes of these vertebrae are as usual very broad, long, and thin; their 
posterior borders concave, their anterior convex, and their postero-external angles pro- 
longed backwards into a short “ styliform ” process, more or less intimately connected 
with the next succeeding vertebra. The horizontal lamellae of the transverse processes of 
the last four vertebrae are pierced by a quite large foramen. 
The superior spinous processes of the vertebrae are so long that they nearly touch 
each other by their anterior and posterior borders; only a slight space being left between 
them. They are quite regularly rectangular in shape, having straight flat superior borders 
at right angles with the anterior and posterior borders. They are connected with each 
other by dense and strong ligaments, and probably become more or less completely an- 
chylosed with age. 
The bodies of the dorsal vertebrae present the usual feature of being exceedingly com- 
pressed, until they are almost vertical laminae of bone. But the most interesting feature 
of this portion of the spinal column is found in the enormous development of the inferior 
or ventral spinous processes. As the bird must be enabled to dart its neck forward with 
great power and rapidity, in the capture of its prey, we find these processes, which are the 
points of origin of the powerful Jongi colli, developed to a corresponding degree. The 
first ventral process consists of two broad thin laminae of bone projecting downwards and 
outwards on either side, divided by a median ridge. These laminm are sessile on the body 
of the vertebra. The second, third, and fourth are more peculiar. A compressed pedicle of 
a length increasing from before backwards, shoots down from the ventral aspect of the body 
of the vertebra, and bears upon its summit two broad, thin, flat lamellae of bone, which, 
divaricating from each other at a very obtuse angle, expand outwards and downwards. 
These aim are largest upon the third dorsal vertebra. Upon the fourth they are smaller; 
and on the fifth, sixth, and seventh become almost atrophied, although the pedicle retains its 
length. The pedicle of the fifth vertebra is the longest. These ventral processes are well 
developed on the first sacral vertebra, are merely a minute projection on the second, and 
totally disappear on the third. 
The movements of this portion of the spinal column are exceedingly restricted, and 
if any exist, they are in a lateral direction. The last cervical vertebra is very freely 
movable in all directions upon the first dorsal. The last dorsal and first sacral have 
also perfect articulating facets; but their spinous processes are so extensively anchylosed, 
that it is probable that but little motion exists between these portions of the spinal 
column. 144 
COUES ON THE OSTEOLOGY 
Sacral vertebrae. I have been unable to determine the exact number of vertebrae which 
compose the sacrum. Including the first three costiferous ones, the number is apparently 
about fifteen. They are throughout completely consolidated with each other, not only by 
their bodies, but by their processes, especially the dorsal spinous ones. The sacrum thus 
formed is exceedingly long and remarkably narrow in shape ; having a lateral anchylosis 
with the iliac bones for nearly its whole extent. It is largest and stoutest opposite the 
acetabula and just posterior to them; where not only the bodies of the vertebrae are 
enlarged, but the long bony ridge produced by the perfect union of the dorsal spinous pro- 
cesses becomes widened and thickened. This long bony spine has but a slight curvature; so 
that while just posterior to the acetabula it is scarcely above the level of the iliac bones, 
yet at both extremities it is elevated some distance above them, by the convexity which 
their upper border presents. On the ventral surface of the sacrum its first three vertebrae 
have their bodies laterally compressed, so that a median ridge is produced analogous to 
that of the dorsal vertebrae. The transverse processes are also tolerably distinct. Just 
posterior to the acetabula, however, the transverse processes are hardly traceable, and 
the body of the sacrum has a median longitudinal furrow, instead of a ridge; more pos- 
teriorly again, the median ridge reappears, and the transverse processes become evident, 
intimately joined with the united ilia and ischia, each one separated from the next by 
an oval foramen. 
Coccygeal vertebrae. There are seven bones in the coccyx, all freely movable upon each 
other. The first two are included between the projecting tubera ischii, which their trans- 
verse processes almost touch. Leaving out of consideration the coccygeal vomer, the 
bones have all the processes of the vertebrae of the other portions of the column. The 
transverse are largest on the fourth and fifth, becoming smaller both anteriorly and pos- 
teriorly. The superior spinous processes are well developed, the more anterior ones 
terminating by tuberculated extremities, which gradually grow smaller, till the last one is 
a simple thin lamella of bone. The inferior or ventral processes are rather stout thick 
tubercles than spinous processes; they are largest posteriorly, and decrease rapidly in size 
from behind forward. 
The “vomer” is of moderate size. Its proximal extremity is deeply concave, bearing 
in its centre the round articulating facet. The thickening of the bone which forms this 
facet is continued along the middle of the bone to the extremity, as a prominent longitu- 
dinal lateral ridge. The superior border is very thin and sharp, nearly straight in outline; 
the inferior border curves gently upwards, and is thickened. The distal extremity is 
simply a small convex nodule, with no projecting process. 
Ribs. The ribs are ten in number. Of these nine articulate with the spine, and 
eight with the sternum. Seven only are dorsal ribs proper; the eighth and ninth being 
articulated with the sacral vertebras posterior to the tip of the crista ilii, and the tenth being 
connected neither with the spine nor sternum. 
The determination of the first rib is rendered very easy and certain, by reason of the 
styliform processes or “ rudimentary cervical ribs ” decreasing rapidly in length from the 
cranial to the caudal end of the cervical vertebras; so that on the last two or three they 
are merely slight pointed tubercles. Then from the first dorsal vertebrae the first rib pro- 
jects as a very slender delicate pointed spicula of bone about two inches long, not reaching 
much more than two thirds the way to the sternum, terminating by a free unattached ex. 
tremity. This rib is also remarkable for the shortness of its neck, and the consequent close OF COLYMBUS TORQUATUS. 
145 
approximation of its articulations with the body and transverse process of the first dorsal 
vertebra. In fact there is only left between them a small oval foramen. 
The six succeeding ribs are the true dorsal ones, and present the characters of the ribs 
proper. Their necks are long and slender, and increase in length from before backwards ; 
they support a head which is but very slightly enlarged. The tubercles of the ribs are 
very large and stout. In fact, these broad, flattened, transverse processes seem almost to 
form the true termination of the ribs, from which the neck and head proper seem but 
offsets. The ribs are very flat antero-posteriorly, and scarcely seem to grow narrower as 
they approach the transverse processes of the vertebras. But from their inner surfaces 
there commences, at some distance from the vertebrae, the projecting ridge which is to be 
continued beyond the transverse processes to form the neck and head. 
As usual, the ribs consist of vertebral and sternal portions, movably articulated with 
each other. Both of these portions grow successively longer from before backwards; but 
the sternal portions much more rapidly than the vertebral. Thus while the sternal portion 
of the second rib is barely three fourths of an inch long, that of the seventh is fully three 
inches. The angle at the junction of these two portions, of course, varies with every stage 
of an inspiration and expiration; but at any given moment the angles become successively 
more acute from before backwards, from the increasing length of the vertebral as well as 
the sternal portions. 
The processes which extend backwards and mesially from the dorsal ribs are well de- 
veloped, extending not only to the next rib behind, but over it to the succeeding inter- 
costal space. They are not straight, but curved, with their concavities towards the spine. 
The first one, that on the second rib, is the shortest, stoutest, and straightest; the others 
become successively longer, slenderer, and more curved, to the penultimate one, but the last 
one is shorter and smaller than it. These processes are at first only ligamentously joined 
with the rib, so that they may be easily broken off from the latter; but with advancing 
age they probably become more or less completely anchylosed. Each process is also 
connected with the rib from which it arises by a broad, dense, aponeurotic membrane of a 
triangular shape, extending from its concave border to its own rib, and along the rib to 
within a short distance of the spine; and with the next succeeding rib by muscular tissue. 
While each is thus firmly and unyieldingly connected with its own rib, it is enabled to as- 
sist the intercostal muscles proper in drawing the succeeding rib towards itself, these slips 
collectively thus exerting no slight force in the respiratory movements of the thorax. 
The two ribs next succeeding the true dorsal, that is, the eighth and ninth pairs, differ 
from the dorsal in their origin, which is from the sacral vertebrm; and in their great length 
and tenuity, especially noticeable in their sternal portions, which are very nearly as long 
as their vertebral. The angle between the two portions is also very acute; but the most 
important difference is, that with the last dorsal ribs the processes just spoken of abruptly 
terminate,— so completely that on the ribs under consideration there is not even a 
rudimentary trace of their existence. 
The last rib differs from all the others in being unattached at either vertebral or sternal 
extremity. It consists merely of two extremely slender elastic bones, tapering to a fine 
point, somewhat larger and broader at their bases, where they are joined to each other. 
The sternal portion is longer than the vertebral. Close by the junction of the two, this 
sternal portion sends off from its posterior border a small, slight process, which curves 
directly outwards and forwards, lying parallel with the posterior border of the rib, which 146 
COUES ON THE OSTEOLOGY 
it joins again about an inch from its origin, leaving a space filled up only by membrane. 
This may very possibly be regarded as the rudiment of an eleventh rib, of which the 
vertebral portion is wholly wanting. It is sometimes entirely obsolete. 
The latter ribs project so far backwards, that the thoracic parietes are prolonged some 
distance behind the acetabula, and consequently the femur in its normal position lies 
directly over the last three or four ribs, and moves backwards and forwards upon them. 
The angle of the last rib reaches within less than two inches of the posterior extremity of 
the elongated obturator foramen. 
Sternum. This bone is sub-rectangular in shape, longer than broad, the greatest length 
being to the average width as two to one. The length in a direct line from the manubrium 
to the tip of the xiphoid cartilage is 7.25 inches; width opposite the superior angles, 3.25; 
width at narrowest part (which is opposite the facet for the sixth rib), 3.00; at widest part 
(opposite the middle of the apophyses), 3.75. Length of keel along its curved edge, 8.40. 
The anterior border is sinuate, projecting at the central line, running backwards as far as 
the groove for the coracoid bones extends, then turning forwards and outwards to the 
anterior angle of the bone. Directly on the median line lies the manubrium, in this genus 
extremely small, merely a slight triangular elevation of bone. The facets for the articu- 
lation of the coracoids are very deep sulci, meeting each other on the median line, and 
extending outwards for two thirds of the width of the bone. The edge of the sternum is 
thick and strong as far as these grooves extend ; externally to them it is merely a thin plane 
bone supporting the costal facets, forming what are called the "costal processes.” 
The lateral edge of the sternum measures five inches in length. It is sinuate as regards 
both a vertical and horizontal plane. It is at first deeply concave, the edge introceding 
towards the central line; but it bulges out again opposite the base of the lateral apophyses, 
and then curves again somewhat towards the central line, producing a convex outline. 
This margin is quite thick anteriorly, but becomes posteriorly exceedingly thin and atten- 
uated. It is marked with articular facets for the sternal ribs; these facets being closely 
aggregated together anteriorly, becoming much further from each other posteriorly till 
they cease opposite the base of the lateral apophysis. 
The posterior margin is a peculiar one; this arising from the great length and width of the 
xiphoid appendage, and the depth of the lateral excavations. Considering the posterior 
margin as beginning with the tips of the lateral apophyses, there is immediately a large 
elliptical excavation an inch and a quarter deep by nearly an inch broad. Across this is 
stretched the ordinary dense semi-transparent membrane. Just at the postero-internal 
border of this excavation there is another notch, but only a very slight one, scarcely a 
tenth of an inch in depth or width. From the edge of this second notch, the posterior 
border of the sternum on each side is regularly convex, meeting on the median line by a 
rounded but somewhat acute angle. This xiphoid appendage is very thin, and curls up- 
wards and backwards from the plane of the sternum. 
Posteriorly, the surface of the sternum is very broad and flat, or even slightly concave; 
anteriorly, it is narrower, and exceedingly concavo-convex, the sides rising upwards from 
the central portion which is thus caused to bulge downwards, with a very convex surface. 
The superior surface of the bone is quite smooth and free from inequalities; the inferior 
surface is marked with various ridges and roughened portions, indicative of the extent of 
origin of the several pectoral muscles. The most conspicuous of these is a ridge running 
obliquely backwards and inwards from the outer angle of the coracoid facet. OF COLYMBUS TORQUATUS. 
147 
The keel begins just posterior to the small rnanubrial process, with a very thick, stout 
margin, which curves with a concave outline downwards and greatly forwards; so that the 
apex of the keel, which is quite acute, projects much in front of the anterior border of the 
sternum. The crest of the keel is regularly a little convex for its anterior half; in 
the rest of the length it is almost perfectly straight, to its subsidence into the level of the 
surface of the bone, which takes place just at the base of the xiphoid. The crest of the 
keel is broader than the vertical portion, and, with the latter, is rough for the attachment 
of the pectoral muscles. The vertical depth of the keel is, just at its anterior extremity, 
very considerable, being nearly one and a half inches; but very quickly, by the great 
Sternum and scapular arch in situ, lateral view, one half natural size. 
(Figure 1.) 
Sternum and scapular arch in situ, from below, one half natural size. 
(Figure 2.) 
downward projection of the body of the bone, joined with the slight convexity of the crest 
of the keel itself) it becomes inconsiderable, and then more gradually decreases as it pro- 
ceeds backwards.. 
Viewing, now, the sternum as a whole, we have to notice how great an extent of surface 
is secured with a trifling increase of weight. Posteriorly, this is attained by means of the 
great lateral projection of the apophyses, as well as by their length, and by the breadth and 
projection backwards of the thin, almost cartilaginous xiphoid. Anteriorly, where the 
sternum is not so wide, the deficiency is atoned for by the great depth of the keel, and 148 
COUES ON THE OSTEOLOGY 
its projection forward; at the same time the outline of the crest of the keel is such that 
when the inequalities of the bone are all filled up with muscular tissue the resulting sur- 
face becomes flat, and broad as well as long, affording the best possible outline for contact 
with the wTater. 
Coracoids. These are very short, and exceedingly broad and stout. Each measures just 
three inches in extreme length. The “ shaft ” proper of the bone is reduced to a minimum 
of length, nearly the whole bone being taken up by the articular and other processes at 
the base and head. 
The base of the bone is expanded into a broad, flat, trapezoidal surface, the sides of the 
trapezoid being all more or less concave. The postero-internal side is concave, smooth, 
and thin, fitting accurately into the articular groove in the sternum. The antero-internal 
border is simply a concave outline, running forward to become the inner edge of the shaft 
of the bone. The antero- and postero-external borders of the trapezoid are the most con- 
cave of all, being formed by a quite acute process of bone which runs directly outwards 
exactly under the costal process of the sternum. 
On the inner aspect of the shaft of the bone, just internal to the coraco-scapular articu- 
lation, there is a lateral expansion of the bone, which curves upwards and forms the pulley 
over which glides the tendon of the pectoralis minor, in its passage to its insertion into the 
head of the humerus. This lateral expansion forms by its superior surface a good part of 
the coraco-scapular articulation. Its inner tip forms a little of the superior coraco-clavicular 
articulation. 
On the shaft of the bone inferiorly there extends downward towards its head a stout 
thick ridge terminating in a convex, somewhat oval process, which bears upon its inner 
face a semilunar facet for the inferior or principal coraco-clavicular articulation. The ex- 
ternal and superior aspect of the bone has a flat broad dilatation terminating in a convex 
facet lined with interarticular fibro-cartilage, forming the inferior half of the glenoid cavity. 
Upon the superior aspect of the shaft, just internal to the preceding facet, there is the 
somewhat semilunar facet for the coraco-scapular articulation. 
Clavicles. These bones are altogether weaker, and meet at a more acute angle, than 
we should expect to find in a bird possessed of the powers of flight of the Loon. The 
angle formed by their divergence is scarcely more than 45°. At their broadest part, which 
is near their origins, they are over half an inch wide, but exceedingly thin. This width 
decreases rapidly towards the symphysis, where the bones are very weak and slender, and 
oval or elliptical on a transverse section. The symphysis is a simple fusion of the two 
clavicles, without any projecting lamella or process, and unconnected except ligamen- 
tously with the apex of the sternal keel. Each of these bones articulates in two places 
with the coracoids, as has been already pointed out. From these articulations the bones 
when in situ dip at first directly downwards, then with a very convex outline run back- 
wards, at last curving upwards again to the symphysis with a considerable degree of 
convexity. From the peculiar articulation of these bones wuth the coracoids at two points 
it results that the curved surface which serves as a pulley for the play of the tendon of the 
pectoralis minor is converted into a complete bony canal. 
Besides the proper articulation of these bones with the coracoids, they are throughout 
their whole extent bound to the latter by a dense layer of fascia, the supraclavicular, 
which is stretched vertically between the bones. 
Scapula. The scapula, as in most birds, is simply a long, narrow, flattish bone, lying OF COLYMBUS TORQUATUS. 
149 
superimposed upon the dorsal aspect of the ribs, nearly parallel with the vertebrae, and 
situate somewhat more than an inch from them. It measures 3.60 inches in length, by 
about one fourth of an inch at its lower, and three fourths at its upper or broadest end. It 
is concavo-convex in two planes: i. e., slightly so in the horizontal plane, its convex edge 
being presented towards the vertebras; and much more decidedly so in a vertical plane, the 
convexity presenting upwards. In the greater portion of its length the transverse section 
of the bone is elliptical or oval; but towards the distal extremity it becomes depressed 
into a simple thin flat lamina. This lamina is nearly straight and very thin, and forms 
the termination of the scapula without curving in any direction. The proximal extremity 
of the bone is much thicker and stronger than the rest. It bends downwards with a very 
considerable, and inwards with a slighter, curve. The thick head of the bone, thus con- 
stituted, articulates with three bones, the clavicle, coracoid, and humerus. 
The claviculo-scapular articulation is a mere apposition of the extreme apex of the clav- 
icle with a very small space just at the internal edge of the head of the scapula, where 
that edge projects inwards upon the expanded lateral process of the coracoid, which forms 
most of the second or superior coraco-clavicular articulation. 
The coraco-scapular articulation is an exceedingly strong and firm apposition of the 
whole head of the scapula with the rough depression on the superior surface of the shaft 
of the bone, just internal and posterior to the glenoid cavity. The articulation seems to 
be essentially almost a synchondrosis. The rough inequalities of the head of one bone are 
perfectly coaptated to those of the other; interarticular fibro-cartilage is interposed; and 
the whole articulation is so firm and unyielding as to permit of but exceedingly limited 
motion, and that chiefly in one direction. That part which the scapula takes in the forma- 
tion of the glenoid cavity constitutes the humero-scapular articulation. The glenoid cavity 
merits special notice. 
When the glenoid facets of the coracoid and scapula are deprived of the dense layer of 
fibro-cartilage which chiefly forms the concavity in which the head of the humerus plays, 
they are found to be perfectly smooth and plane. Both are tolerably regularly oval in 
shape, the coracoid the larger, and quite oval, the scapular smaller, and more of an 
elongated and subtriangular shape. The coracoid facet is horizontal antero-posteriorly, 
with transversely an obliquity of about 45° upwards and outwards; the scapular is about 
perpendicular to it, with transversely 45° of obliquity forwards and outwards. Upon this 
osseous basis a very dense and thick layer of unyielding fibro-cartilage is superimposed, to 
form the slight concavity which exists for the reception of the head of the humerus. This 
cartilage is laid over the whole of both facets, but is much the thickest at their margins, 
where it rises with a well-defined edge, leaving a central depression which constitutes the 
true glenoid “ cavity.” This cavity is very broadly semilunar in shape, the cornua of the 
semilune having quite well-defined, raised borders, its convexity being but slightly, and 
its concavity scarcely at all, elevated. But the depression is so slight that the entire cavity 
is able to contain but a comparatively small portion of the articular head of the humerus. 
This disposition of the elements of the articulation, as well as the shape of the head of the 
humerus, is plainly indicative of the design of the joint,— the attainment of great free- 
dom of motion in all directions by some sacrifice of strength. A comparison of the 
glenoid with the cotyloid cavities of this bird furnishes a striking illustration of the pre- 
ponderance of mobility over stability which usually obtains in the anterior extremities of the 
hio-her vertebrates. 
D 150 
COUES ON THE OSTEOLOGY 
The disposition of the fibro-cartilage above noticed, by which the glenoid cavity is aug- 
mented in depth, is strictly homologous with the raised border of cartilage which surrounds 
the same cavity in man, and which subserves the same purpose. The same plan, accord- 
ing to Owen,1 exists throughout the lower orders of birds, the Rasores, Natatores, and Oral- 
latores; while in the more highly organized birds, the Raptores and Insessores, there is 
found a distinct bone, the “os scapulare,” or “os limnero-scapulare,” which subserves the 
same purpose. 
Humerus. This hone is moderately long for the size of the bird, but quite stout and 
strong, and especially notable for the extensive development of the crests and processes 
near its proximal extremity. It measures between seven and a quarter and seven and a 
half inches in extreme length. The shaft is centrally very nearly circular on a section; 
towards both extremities of the bone it soon becomes flattened in a plane about half-way 
between the vertical and horizontal,—at the distal extremity to form the two condyles; 
at the proximal, to expand into the well-marked superior and inferior crests. The superior 
crest is very high and long, extending from the articular head to beyond the middle of the 
bone before it is obliterated; but it is only conspicuously elevated for about one and a half 
inches of its length, for the greater part of which extent it affords attachment to the broad 
tendon of the great pectoral. Mesial to this crest, on the shaft of the bone, about an inch 
from the head, is the small tubercle for the attachment of the conjoined tendinous slips 
from the latissimus dorsi and the long extensor cubiti. The inferior crest curves as usual 
in the opposite direction from the superior. It is much shorter, broader, and thicker than 
the superior, and is placed obliquely to the shaft of the bone, that is to say, parallel with 
the inward inflexion of the proximal end of the shaft towards the glenoid cavity. Its under 
surface presents well marked the ordinary deep fossa; its superior surface near the articular 
head of the bone also another fossa, more shallow, however, than the inferior. The proximal 
extremities of both of these crests are marked with several tubercles and facets for the 
insertion of various muscles, the majority of all the muscles which act upon the humerus 
being inserted into one or the other of them. 
Between the proximal extremities of these crests is situate the articular head of the bone. 
It is of an oval shape, exceedingly convex in its transverse, less so in its longitudinal axis. 
Its face is placed obliquely with reference to the shaft of the bone, from the fact of that 
part of the bone which supports it curving inwards to meet the glenoid cavity. Its long 
axis, which is placed directly between the extremities of the superior and inferior crests, is 
not quite vertical, but inclines obliquely outwards and upwards. The nature of its con- 
nection with, and movements in, the glenoid cavity, have already been adverted to. 
The distal extremity of the bone presents well marked the great peculiarity which 
characterizes the elbow-joint of the class Aves; namely, the hemispherical tubercle for the 
ulnar articulation, and the elongated oblique tubercle, extending somewhat along the shaft 
of the bone, over which the radius moves. The necessity for the very peculiar shape of 
these articulating facets arises from the obliquity of their plane in relation to the plane of 
the circle which the ulna and radius describe in the unfolding of the wing. The articular 
facets do not project directly outwards, but obliquely downwards and outwards, so that, in 
the folded wing, the distal extremities of the ulna and radius are below the level of and 
external to the proximal extremity of the humerus. Now, in extension of the forearm, by 
the peculiar motion which the radius has over the elongated oblique tubercle with which 
1 In Todd’s Cyclopaedia of Anatomy and Physiology, Article Aves. OF COLYMBUS TORQUATUS. 
151 
it articulates, its distal extremity describes a greater arc of a circle than does that of the 
ulna; so that, although the plane of the circle in which these bones move is oblique to the 
axis of the humerus, yet during extension this obliquity becomes gradually less and less, 
until at full extension it quite disappears, and the bones of the arm and forearm lie in the 
same plane. 
It is exceedingly interesting to compare this articulation with the elbow-joint in the 
human species. In the latter, the connection between the ulna and humerus is most strictly 
ginglymoid, admitting of only backward and forward motion; while pronation and supina- 
tion are perfect, by the very free rotation of the radius upon the outer tuberosity of the 
humerus, and around the distal extremity of the ulna; but the radius also has, in common 
with the ulna, the ordinary ginglymoid movements of flexion and extension. Thus the 
elbow-joint, taken as a whole, and considered with reference to the movement of the fore- 
arm upon the arm, is strictly a ginglymus, notwithstanding the element of the diarthrosis 
rotatorius of the head of the radius. In birds, although pronator and supinator muscles 
exist, yet they seem to serve rather to steady the radius than to move it, and the prona- 
tion and supination of the forearm is exceedingly limited, if indeed it exist at all. While, 
therefore, the axes of the two bones of the forearm scarcely change their relations to each 
other, the common plane of their two axes is continually changing its relation to the 
axis of the humerus, in flexion and extension of the forearm. This peculiar character of 
the movements of the forearm is arrived at by the complete obliteration of the element 
of rotation in the humero-radial articulation, and the conversion of the direct antero- 
posterior ginglymoid motion into an oblique ginglymus. As the ulna must of course 
accompany the radius in this obliquity of its flexion and extension, the deep sigmoid cavity 
is converted into a shallow circular depression, which receives the small hemispherical 
articulating facet of the humerus. By this means it can adapt its motions to any degree 
of obliquity which may be impressed upon it by the position of the radial articulating 
surface. 
Another interesting feature in this joint is that it is not the head of the radius alone 
which articulates with the radial facet of the humerus. That part of the head of the ulna 
which lies immediately above and posterior to the radio-ulnar also plays over this outer 
oblique tuberosity of the humerus, forming with the rounded head of the radius an 
elongated depression, which accommodates itself to this elongated radial facet. In this 
feature of the articulation of the head of the principal bone of a limb with loth the 
condyles of the bone above it, is seen an indication of what exists in the femoro-tibial 
articulation of the human species; and since it seems to denote a tendency of the element 
of stability to preponderate over that of mobility, it is what we might expect to find when 
we remember how fixed the radius is to the ulna, causing the motion of the forearm to be 
limited to flexion and extension. 
The posterior aspect of the end of the bone presents two well-marked longitudinal 
grooves, completely separated from each other by a median ridge. These grooves give 
passage to the tendons of the two extensor muscles of the forearm, proceeding to be 
inserted respectively into the outer and inner sides of the olecranon. The olecranonoid 
depression is hardly recognizable as such; and the coronoid is but slightly marked. 
Ulna. As usual, much larger throughout its whole extent than the radius, and quite as 
large at its distal as at its proximal extremity. It is a little less than six inches long. Its 
shaft is considerably curved in its whole length, subcircular on section, being flattened 152 
COUES ON THE OSTEOLOGY 
along its inner aspect. Its external border is marked by Oblique ridges corresponding 
to the insertions of the secondary quills. The olecranon is a somewhat compressed process 
at the posterior aspect of the head of the bone, but does not extend above the margins of 
the articular cavity. This latter is placed upon the inner and anterior aspect of the head 
of the bone, and has been already described. Just external to, and below it, is the radio- 
ulnar articulation. It is merely a slight subtriangular depression, against which the head 
of the radius is apposed, and has leading from its superior margin the continuation of the 
facet on the head of the radius, for articulation with the external oblique tuberosity of the 
humerus. Both lateral surfaces of the head of the ulna are rough, for the attachment of 
muscles. 
The distal extremity of the ulna is fully as large as the proximal, but of quite a different 
shape. It is greatly flattened horizontally, the anterior margin projecting forwards as a flat 
ridge, over the superior surface of which passes the radius. The articulation of the radius 
with the ulna is however merely by a small facet on the middle of this superior aspect of 
the head of the bone. The greater part of the remaining surface of the head of the bone 
forms a smooth, somewdiat semilunar depression, by which it is articulated, partly with the 
posterior half of the head of the metacarpal bone, and partly with the small carpal bone, as 
is more particularly described further on. 
Radius. The radius is exactly of the same length as the ulna, but much smaller than it 
throughout its whole extent. It is quite straight except just at its distal extremity, where 
it is somewhat decurved to overlap the extremity of the ulna. Towards its lower extremity 
it increases in size, though not to any great degree, and becomes horizontally flattened. 
Its rounded head, considerably larger than the shaft below it, bears upon its inferior 
border the small ulnar articulating facet, and upon its face the much larger and somewhat 
oval depression for articulation with the humerus. Its distal extremity is marked supe- 
riorly with a very deep groove, wThich continues for some distance up the shaft for the 
lodgment of the tendon of the extensor metacarpi radialis. Just internal to it is another 
groove, but much shorter and less conspicuous. 
The radius articulates below wdth the ulna, as already described; but its principal articu- 
lation is with the large bone of the carpus. Nearly the whole of its extremity is occupied 
by an oval facet, long in its horizontal diameter and transversely very convex, which is 
received into the deep concavity on the radial aspect of the carpal bone. This radio-carpal 
articulation presents just the opposite feature from that of man, a convexity of the end of 
the radius being received into a concavity in the carpal bone, instead of the reverse. 
Bones of the Carpus. Of the two carpal bones, that corresponding to the scaphoid, semilu- 
nar, and cuneiform, is the largest, and articulates chiefly with the radius. It is wedged in at 
the outer angle of the joint between the metacarpal bone and the radius, extending far 
enough towards the ulnar side of the joint to articulate with the ulna by a small facet. 
It is of a very irregular shape, marked with three facets, for articulation respectively 
with the radius, ulna, and metacarpus, and with two deep grooves for the lodgement of 
tendons. 
The deep radial facet has been already noticed. Just on the opposite side from it, 
the face of the bone presents the smooth depression for the reception of the head of the 
metacarpus; this facet is divided into two parts by a vertical median ridge, corresponding 
to the vertical depression in the head of the metacarpus. The very small facet upon the 
interno-posterior aspect of the bone articulates with the radial edge of the large terminal 
facet of the ulna. OF COLYMBUS TORQUATUS 
153 
Upon the superior surface of the bone there runs longitudinally the continuation of the 
deep groove of the radius which lodges the extensor inetacarpi radialis. At right angles 
with this and running transversely, there is a still deeper groove which conducts the ten- 
don of the flexor inetacarpi radialis. 
The second, smaller bone of the carpus, which represents the second row of carpal bones, 
is placed just in the bend of the joint, on the ulnar side, wedged in between the ulna and 
metacarpus, with both of which it articulates. Its ulnar aspect presents a smooth, oval, 
somewhat depressed facet, which plays against the extremity of the large articulating 
surface of the ulna. Its metacarpal aspect presents a very deep horizontal notch or fis- 
sure, into which is received the inferior thin border of the metacarpal bone. In flexion 
and extension of the metacarpus, this small bone rides backwards and forwards along the 
edge of the metacarpal bone, being as it were astride of the latter. The non-articular 
aspects of the bone are rough for the attachment of tendons. 
Metacarpus. In the single metacarpal bone, which, as in all birds, results from the fusion 
of the five of the human species, there may be clearly traced three distinct bones. 
The first, which corresponds to the metacarpal of the thumb, is found superimposed upon 
the radial edge of the metacarpus, and intimately blended with it, appearing like an elevated 
crest. It is about one and a half inches long, and bears upon its distal extremity the pollex 
or thumb. 
The second, or metacarpal of the little finger, lies directly upon the ulnar side of the bone, 
and is much more distinct than the preceding. It is from its origin for about half an inch, 
fused with the main bone, but then becomes entirely separated from the latter by a 
considerable hiatus, running forward to be again united to it about half an inch from its 
distal extremity. It supports upon its tip the “ulnar finger.” 
The remaining greater portion of the metacarpus results from the coalescence of the 
three middle bones of the human hand. This supports the three phalanges of the “ radial 
finorer,” and articulates with the radius and ulna. 
O 7 
The metacarpus, thus constituted, is a strong bone, nearly four inches long by about five 
eighths of an inch broad at the broadest part, much compressed. Its proximal extremity is 
taken up wholly by a single large, smooth, articulating facet, which moves upon the ulna 
and both of the carpal bones, but has no connection with the radius, the large carpal bone 
being interposed between it and the head of the latter. This articulating surface is 
exceedingly convex from the radial to the ulnar side; but presents in the median line 
a deep sulcus running its whole length, causing the transverse outline of the head to be 
concave. The greater part of the head is joined by a strictly ginglymoid articulation to 
the central portion of the large facet on the ulna. At the radial side the articulation is 
with the large carpal bone; at the ulnar, the inferior border is prolonged backwards, and 
forms the prominent ridge over which rides the smaller carpal bone, as already described. 
On either side of the articulating surface the bone presents rough elevations and depres- 
sions for the insertion of tendons and ligaments. On its superior aspect the bone is also 
marked with several longitudinal grooves, which lodge the tendons that are inserted into 
the phalanges. 
Phalanges. The pollex, or thumb, is a short, perfectly straight bone, which projects one 
inch beyond the abrupt termination of the crest-like elevation corresponding to the first 
metacarpal bone. It is much compressed laterally, and terminates in a truncated sharp 
edge. It is movably articulated with the metacarpal bone, but really has but very slight 
motion. 154 
COUES ON THE OSTEOLOGY 
The third or “ ulnar finger ” is a single short, slight phalanx, about half an inch long. 
It proceeds from the extremity of the ulnar metacarpal, with which it is articulated, but 
is so firmly bound by ligaments to the under edge of the first phalanx of the larger 
radial finger that it enjoys little or no motion. 
The middle or “ radial finger ” forms the proper continuation of the hand. It consists 
of three phalanges. The first is of considerable size, being one and a quarter inches long, 
its radial side thick and flat, and separated by quite distinct borders from the thin lamelloid 
expansion on its ulnar aspect. Its proximal end articulates with the distal extremity of 
the metacarpus by a slightly depressed and irregular surface. The second phalanx is much 
smaller, though of about the same length as the preceding, from which it differs chiefly in 
not having the compressed lamella of bone proceeding from its ulnar aspect. It articulates 
with the preceding by an enlarged head. The third phalanx is merely a very small, insig- 
nificant, acutely pointed spicula of bone, scarcely a third of an inch long. 
Ossa innominata. The innominate bones are remarkable for their great length antero- 
posteriorly, as well as for their extreme narrowness and the straightness of their longitu- 
dinal axis, which latter is scarcely more curved than is that of the sacrum itself. They 
measure, from the tip of the ilium to the tuberosity of the ischium, six and a half inches; 
and they extend from the interspace between the sixth and seventh ribs to that between 
the second and third coccygeal vertebrae. Throughout this extent, they are very closely 
apposed to, and lie parallel with, the spine ; and they are completely anchylosed with 
it, except for about half an inch at each extremity. Besides the want of antero-pos- 
terior curvature, the bones leaving out of consideration the rami of the pubes, which 
are curved towards each other on the median line—have little or no lateral convexity. 
They converge towards each other on the spine, at an angle of about 50°, forming a 
greatly elongated, very narrow pelvis; which, by the flattened shape of the ischia is quite 
deep and transversely triangular posteriorly, but which, more anteriorly, by the termina- 
tion of the pubes at the acetabula, and the outward expansion of the ilia, becomes so 
shallow as quite to lose its characteristics as a “cavity.” On the median line, the ilia, as 
usual in the class, do not meet, but are throughout separated by the anchylosed spinous 
processes of the sacral vertebrm. The approximation of the two cristae ilii is greatest just 
posterior to the ischiadic foramen; both anterior and posterior to this point the bones 
slightly recede from the median line of the vertebrae, the amount of divergence gradually 
increasing, until the tips of the ilia are three fourths of an inch, and the tubera ischii one 
half an inch, from the median line. 
Ilium. This portion of the os innominatum is, anteriorly to the acetabulum, a very thin, 
narrow, osseous prolongation, extending forwards and a little outwards as far as the seventh 
rib. It is externally concave antero-posteriorly, and also laterally very slightly so. It is 
completely anchylosed, to within less than one half an inch of the tip, with the trans- 
verse processes of the sacral vertebrae over which it is imposed. It has no connection, 
however, with the last ribs, though these pass out so close beneath it that they almost 
touch its internal surface. Towards the acetabulum the bone spreads out as a stout curve, 
which meets a similar projection from the ischio-pubic bone, and then completes the circle 
of the acetabulum. Just above the ring, the acetabulum proper, the bone becomes very 
thick and strong, and is elevated into a projection wdiich overhangs as it were the cotyloid 
cavity. This eminence is suboval in shape; and bears upon its summit a flat, smooth, 
articular facet, continuous with the articular surface of the acetabulum proper, to which is OF COLYMBUS TORQUATUS. 
155 
apposed the superior surface of the trochanter major of the femur. The ilium posterior 
to the cotyloid cavity continues along the spine as a simple prolongation of bone for about 
an inch, after which it is completely fused with the ischium for the rest of its extent. 
The ordinary ischiatic notch of man is thus converted into a foramen. The foramen in 
this instance is of an oval shape, three fourths of an inch long, by one third in diameter, 
lying mesially to the obturator foramen at its commencement, just posterior to the cotyle, 
and close to the spine. 
Ischium. The ischium is quite flat, scarcely presenting a concavity or convexity in any 
direction. Its mesial border is completely fused with the ilium, except anteriorly where 
it separates from that bone to form the ischiatic foramen, and runs forward as a slender 
process, separating the ischiatic from the obturator foramen, to the acetabulum, which as 
usual it assists in forming. Posteriorly, the bone is prolonged, forming quite a long and 
narrow but stout process, terminating in the tuber ischii, lying close alongside of the 
transverse processes of the two first coccygeal vertebrae, but not united with them. 
Between this projection and the process which curves forwards and outwards to meet the 
pubes there is a deep semilunar sulcus. The external border of the bone is long and 
concave, the latter especially at its extremities, this concave border forming the mesial 
margin of the obturator foramen. 
Os pubis. This is a long and exceedingly slender bone. Its anterior extremity, which 
contributes its share in the formation of the acetabulum, is tolerably broad and strong; 
but the bone immediately becomes contracted to a slender straight spiculum, which extends 
between the acetabulum and the projecting process of the ischium, forming the external 
border of the obturator foramen. With the tip of this projecting process, which seems to 
represent in part at least our “ ascending ramus of the pubes,” the bone is movably connected 
by ligaments. From this point the bone curves quite abruptly mesiad to meet its fellow. 
It becomes at the same time broad and thin, the breadth increasing suddenly towards 
the end, so that the bone terminates by a wide, rounded, club-shaped free extremity. 
As usual in the class, there is no symphysis pubis, though the two bones closely approach 
each other. 
The shape and position, as well as the connections of the os pubis with the rest of the 
pelvis, are such that the free extremities of the bone must be approximated or separated 
chiefly by the elasticity of torsion of the slender shaft of the bone. 
Acetabulum. The acetabulum has quite lost its character as a a cotyloid cavity,” and 
become a simple ring of bone. The floor of the cavity is so entirely wanting, that the 
internal diameter of the acetabular ring is nearly as great as the external. The outer 
border of the ring is a well-defined, elevated osseous ridge,—most marked posteriorly and 
externally, but sinking somewhat towards the mesial line. The globular head of the 
femur is prevented from sinking through this ring by the abutment and articulation of 
its trochanter major with the prominent facet already described as lying above the cotyle. 
The smooth articular surface of the acetabulum is continued uninterruptedly on to this 
facet, so that the articulation of the head and trochanter of the femur is really only 
a single joint. The exact character of the motions resulting from this joint will be 
described in speaking of the femur. 156 
COUES ON THE OSTEOLOGY 
Of the Loiver Extremities. 
In the upper extremities of the bird, although there is much interesting mechanism 
displayed, yet the various features are in general only such as are found in the wings of the 
greater number of the groups of the order. The very peculiar type of structure which 
stamps such an individuality upon the Colymbidce, Podicipidce, and, to a somewhat less extent, 
upon the brachypterous Natatores generally, does not extend in any very marked degree 
into the superior extremities. It is in the morphology of the posterior extremities, both 
as regards the osseous framework and the muscles by which the bones are moved, that we 
find the most marked peculiarities of structure. When we recollect how very peculiar are 
the form and position of the posterior extremities, both as regards the axis of the bird’s 
body, and its centre of gravity, causing progression on land to be awkward and laborious 
from the stiff and constrained position in which the body must be placed to bring the 
centre of gravity within the base of support, we might naturally expect to find interesting 
peculiarities in the structure of these extremities. Such is really the case; the whole 
morphology of the posterior limbs being so moulded as to obtain the most advantageous 
structure possible for propelling the bird over and through the water, at a considerable 
sacrifice of ease and power of terrestrial locomotion. 
This indication, which we see more or less completely fulfilled throughout the Natatores 
brachypteri, is perhaps more strongly pronounced among the Colymbidce than in any other 
family of birds, with the exception of course of the Penguins, (Aptenodytes, Spheniscus, &c.,) 
and certainly reaches the maximum of development which is found among any birds that 
retain the power of aerial locomotion. The species of bird now under consideration being 
typical, so to speak, of the whole family, in it we can study this peculiar type of structure 
to great advantage. 
In examining the morphology and functions of the lower extremities, we must of course 
consider them with reference to their action upon that element to which they are specially 
adapted, the water. To produce a perfect pair of paddles, three indications must be 
fulfilled. First, the limbs must be articulated far backwards, and, while they have the 
freest motion, must be so abducted from the median line that the broad webs shall not 
interfere with each other. Secondly, in the backward stroke the broadest possible surface 
must be attained for action upon the water, while in bringing the leg forward exactly 
the reverse must be the case. Thirdly, the great power of the legs must be chiefly 
exerted in pushing; and hence the bulk of the muscles must be upon the posterior 
aspect of the several components of the legs. The mode in which this latter indication 
is fulfilled will be noticed in the description of the muscles. The first two may here be 
considered. 
Femur. This bone is remarkably short and stout. It measures only two inches in en- 
tire length, while across the condyles it is three fourths of an inch, or more than a quarter 
of its total length. The width across the upper extremity, from the trochanter to the 
globular head, is fully half an inch. The shaft is also exceedingly stout, and much 
curved, the convexity presenting forward. It is marked along the entire length of its 
posterior aspect, as well as over the trochanter and on the sides of the condyles, with 
roughened tubercles and depressions for the attachment of the various muscles which act 
upon it. 
The globular “caput femoris” is peculiar both in shape and position. It projects almost OF COLYMBUS TORQUATUS. 
157 
at right angles from the inner aspect of the proximal extremity of the bone. The neck, 
however, is so very short and thick, and projects so directly inwards, that the head appears 
to be little more than a stout process of bone. It is, moreover, placed so low down on the 
femur, that the great trochanter rises very considerably above its level. Its summit is as 
usual occupied by a fossa for the insertion of the ligamentum teres. 
The trochanter extends upwards and outwards as a stout, somewhat pointed process, 
and is so large as to seem to form the real “ head ” of the bone; from the inner aspect 
of it the real head appears as a short stout offset. The non-articular surfaces of the 
trochanter are all roughened for the attachment of muscles. There is no trochanter 
minor. 
The hip-joint is an exceedingly peculiar and interesting one, from the extent of the 
trochanteric articulation. The smooth articulating surface of the globular head of the bone 
is on the superior aspect continued uninterruptedly along the neck of the femur, to spread 
out on the top of the trochanter into a large, smooth, plane facet, which occupies nearly all 
the superior surface of that process. 
When the head of the bone is inserted into the circular ring which constitutes the 
acetabulum, this articulating surface of the trochanter is applied closely to the smooth facet 
which, as already described, lies above and a little behind the acetabulum, appearing like a 
continuation from it, which in effect it really is. This abutment of the trochanter against 
the ilium prevents the small head of the bone from sinking too deep into the cotyle, which 
it would otherwise do from the very deficient character of this cavity; and, moreover, 
upon it seems to be borne the chief pressure of the weight of the body in some of its 
attitudes. 
From this peculiar construction of the hip-joint, it results that a particular direction is 
given to the position, and all movements of the femur, and that motion in some directions 
must be exceedingly free, while in others it is greatly restricted, or wholly arrested. From 
the direction in which the plane of the trochanteric facet is situated, it results that the most 
natural and unconstrained position of the femur is outwards, forwards, and downwards, at 
an angle of about 45° in each of these axes. This remarkable outward position, or great 
amount of abduction, is necessary to enable the femur to clear the long ribs which project 
outwards and backwards along its inner aspect, and also contributes its share towards the 
wide separation of the feet. From this state of permanent abduction, any adduction, or any 
further abduction, are equally impossible; for the first would draw away the trochanter 
directly from its articulation, the latter would pull the globular head directly out of the 
cotyloid ring. Therefore, though muscles exist which arise from the horizontal ramus of 
the pubes and are inserted into the femur at various points, and which are really the 
analogues of our pectineus, adductors, etc., still, their line of traction, resulting from the 
shape of the pelvis and position of the femur, is such that they pull it almost directly 
backwards, having little if any adducting power. 
Antero-posteriorly, the normal position of the femur seems to be in a state of semi-flexion 
forward at an angle of about 45°, with of course the divergence downwards and outwards 
before mentioned. From this position the movements of flexion and extension are quite 
free, the former particularly so. 
The element of rotation is a very prominent one in the motions of the hip-joint, affording, 
as we shall presently see, the beginning of the very extensive power of rotation which the 
whole limb enjoys. A special muscle, the obturator, inserted into the tip of the trochanter, 158 
COUES ON THE OSTEOLOGY 
would seem to preside especially over the outward rotation ; besides which various 
flexors, extensors, glutasi, etc., are made to act either as external or internal rotators, by 
some peculiarity in their insertion into the femur. 
In the positions and movements of the femur we see its perfect adaptation to the 
functions it has to perform, those of affording a short, stout point d’appui for the leg, at 
a sufficient distance from the body, and of powerfully impressing upon the distal segments 
of the lower extremity antero-posterior and rotatory motions; this force of motion decreas- 
ing as we proceed from the body just in proportion as extent of motion is augmented. It 
would not seem that the length of the first segment of a limb is an indication of the 
powers of that extremity. Thus among the Cypselidce and the Trochilidce, whose powers 
of flight are unsurpassed, the humerus is very short; but in them, as in the case before us 
of the Loon’s femur, the primary segment is most powerfully acted upon by large muscles, 
which force of motion is by a common law of mechanics converted by the long distal 
segments into extent and rapidity of motion. 
The distal extremity of the femur is no less interesting than the proximal. The shape 
of the two condyles, as well as of the articulating surfaces themselves, is very different. 
The external condyle is very much the larger of the two, projecting more outwards and 
as much further downwards than the internal one, as from the obliquity of the femur it is 
necessary to bring the faces of the two upon the same plane.1 Its articulating surface is 
longitudinally very convex, transversely equally concave, by a rounded sulcus, which 
causes its convexity to present a ridge on each side. This is the true articular surface of 
the outer condyle, and it is closely coaptated with the head of the fibula. Upon the 
internal side of the condyle there is also, however, a facet of an oval shape, which articu- 
lates with a corresponding facet on the fibular edge of the head of the tibia. The proper 
femoro-tibial articulation is however with the internal condyle. The latter is much less 
irregular than the outer one, having simply an oval extremity, convex in both its axes, 
which rests upon the very slightly depressed, broad, flat head of the tibia. The movements 
of the knee-joint will be spoken of after noticing the bones of the leg. 
Tibia. This bone is very long, measuring with its spine seven and a half inches, and 
consequently containing the length of the femur nearly four times. Its spine is just two 
inches long, leaving a length of five and a half inches for the tibia proper. Below, it is 
flattened antero-posteriorly, indicating its further expansion into the two condyles 
(“malleoli”). More superiorly, it becomes sub-quadrilateral. The outer posterior edge 
forms for nearly its whole extent the fibular anchylosis. The inner anterior edge is the 
most prominent. About one and a half inches below the head of the bone it rises as a 
very prominent thin crest, with a sharp margin. This crest curls over forwards more and 
more, until it has on its anterior aspect a deep longitudinal concavity, and, preserving much 
this shape, is prolonged two inches above the head of the bone as an exceedingly prominent 
spine. The posterior aspect of this spine is at its base prolonged directly from the articular 
head of the bone, forming a deeply concave continuation of the joint, exactly resembling 
the olecranon of the human species.2 Indeed, this articulating surface of the tibia has 
almost exactly the shape and general appearance of the sigmoid cavity of our ulna. The 
1 Prof. Owen considers our olecranon to be not a patella 
joined to the ulna, but as rather analogous to the structure we 
are now considering. 
2 This difference in the length of the two condyles, to atone 
for the obliquity of the shaft of the femur, is precisely upon the 
same principle as in man, but the case is exactly reversed, 
since, as the femur is permanently abducted, instead of ad- 
ducted, the outer condyle instead of the inner must be the 
longest. OF COLYMBUS TORQUATUS. 
159 
entire surface of the spine presents roughened elevations and depressions for the attach- 
ment of muscles. The oval concave head of the fibula, placed on the external aspect, 
completes the crural elements of the knee-joint. 
Just at the superior border of the joint there is a very small projecting process of bone, 
which is generally regarded as the true analogue of the patella. 
The twofold design of this elongated spine is quite evident. In the first place, by the 
simplest mechanical law, it increases greatly the power of the extensor muscle, the 
cruraeus, coming down over the front of the femur. Secondly, some of the most power- 
ful of the muscles which act upon the metatarsus take their origin primarily from its 
extreme tip, and the consequent increased length of fleshy bellies which they thus 
acquire gives them an equal increase of space for contraction. 
The construction and movement of the knee-joint present several interesting peculiari- 
ties. Although both condyles of the femur articulate with the tibia, the most extensive 
articulation of the outer one is with the head of the fibula, upon which it principally 
rests. In this bird, however, while flexion and extension of course form the most promi- 
nent elements in the motion of the leg upon the thigh, to these there is superadded a very 
considerable degree of true rotatory motion, also quite different from the peculiar obliquity 
of motion which obtains in the elbow-joint. 
The ordinary position of the leg, with reference to the axis of the body, when least 
influenced by muscular action, is to lie not very far from horizontally backwards, with 
some degree of inclination downwards, and a greater amount of obliquity outwards. 
When the leg is strongly flexed, it results, from the peculiar direction of the femur 
from the body and from the plane of the femoral condyles, that the leg becomes quite par- 
allel with the axis of the body, while its outward inclination is totally lost. The legs in a 
fresh specimen may be easily made to touch each other over the coccygeal vertebrae. Con- 
versely, with strong extension, the axis of the leg becomes more and more nearly perpen- 
dicular to the axis of the spine, while its amount of abduction from the body is constantly 
augmented. These are the positions consequent upon simple flexion and extension. 
In the ordinary semi-flexed position of the leg, the plane of the condyles with which 
the metatarsus articulates, is placed obliquely outwards instead of directly forwards, so 
that the metatarsus projects outwards from the body; and the fibula, especially at its 
upper part, is rather upon the posterior than the directly external aspect of the leg. 
Now, when the leg is drawn forwards, the same muscles are so inserted that they cause a 
rotatory motion (chiefly in the knee-joint), which brings the fibula directly outwards, the 
plane of the tibial condyles directly forwards, and consequently the sharp anterior edge 
of the metatarsus, and the anterior surface of the closed toes, cut easily through the water 
with but slight resistance. 
Although the femur participates in this rotatory motion of the lower extremities, yet the 
rotation is still greater in the knee-joint. From the construction of the joint, remem- 
bering the broad flat head of the tibia on which the convex internal condyle rests, and the 
much more intimate coaptation of the head of the fibula with the external condyle, it 
seems probable that the extremity of the fibula is chiefly the pivot around which the 
motion of the knee-joint takes place. Several muscles of the leg seem to act solely as 
rotators, while many of the flexors and extensors are so inserted as to have some such 
action. 
The two condyles at the distal extremity of the tibia forming the “ malleoli,” are very 160 
COUES ON THE OSTEOLOGY 
prominent and convex, with a deep sulcus between them. They much resemble, in general 
appearance, the condyles of the human femur; but are laterally more compressed, and the 
sulcus between them is wider. It is remarkable that the internal one is the largest and 
longest, so that the obliquity of the tibia in relation to the axis of the body, instead of 
being corrected in the metatarsus, is increased, and the foot thrown still further outwards. 
On the posterior aspect, the condyles continue upwards for some distance, as prominent 
narrow ridges, serving to confine the very numerous tendons which pass down over the 
heel. The sides of the condyles are rough for ligamentous attachment. Just above the 
condyles, on the anterior face of the bone, is the depression ordinarily met with, crossed by 
a very distinct though small bridge of bone, forming a canal through which the extensor 
tendon of the toes passes. 
Fibula. This is as usual a tapering bone, not extending the whole length of the tibia, and 
attached to its outer and somewhat posterior aspect. Its head is quite distinct, lying just 
at the edge of the head of the tibia, receiving the greater part of the outer condyle of the 
femur. For an inch or so, it is quite separate from the tibia; is then united with it for 
some distance, becomes again distinct for about an inch, and then finally merges as a slender 
spiculum into the side of the tibia, rather more than an inch above the joint. A slight crest, 
however, gives an indication of it, which can be traced quite to the external malleolus of 
the tibia. 
“ Tarso-metatarsus.” The next segment of the lower extremities results, as in most if not 
all birds, from the fusion of the elements of the tarsus and metatarsus proper.1 In this 
species it is an exceedingly compressed bone three and a half inches in length; its sides 
nearly smooth and quite flat; its anterior and posterior borders grooved for the reception 
respectively of the extensor and flexor tendons ; and separated from the sides by remark- 
ably sharp edges. These edges are so prominent that they impress a very decidedly rec- 
tangular shape upon a transverse section of the shaft of the bone. By these grooves, and 
the fibrous thecae, which their sharp edges give origin to, the tendons are prevented from 
encroaching in the least on the sides of the tarsus, which is thus enabled to keep its ex- 
ceeding thinness; while at the same time they serve to increase greatly the antero-posterior 
width of this segment of the leg. 
The process of bone representing the os calcis, rises at the superior end of the bone, on 
its posterior aspect, as a very conspicuous crest. It is of quite a regular square shape, 
about a third of an inch long, and of about the same height. The groove denoting its line 
of fusion with the metatarsus may be traced along its base. Into it are inserted the two ten- 
dons of the gastrocnemii; and its substance is perforated by longitudinal canals, through 
which pass the flexor tendons of the toes. The most posterior of these canals is very large, 
and transmits the majority of these tendons ; anterior to it, that is between it and the meta- 
tarsus, are two or three very small canals, lying side by side on the same plane. 
The proximal extremity of the bone is marked on each side of the median line by two 
oval depressions, in which are received the condyles of the tibia. In shape and position the 
two differ slightly from each other, in consequence of a corresponding difference in the two 
condyles of the tibia. On either side of the head are the roughened elevations for ligamen- 
tous attachments, and for the tendons of the tibialis posticus and peroneal muscles. 
The metatarso-phalangeal articulation is extremely interesting. If we examine the foot of 
1 This segment is, by ornithological writers, universally called 
the “ tarsus.” Although this name is obviously incorrect, yet 
in our ordinary zoological descriptions of birds, it would seem 
hardly worth while to reject it in order to apply to it its more 
strictly proper designation of tarso-metatarsus. OF COLYMBUS TORQUATUS. 
161 
the bird in a fresh state, we find, on closing the anterior toes, that they do not lie all beside 
each other; but that the inner one lies almost directly behind and between the other two. 
This arrangement of the toes is in order that the least possible resistance to the water shall 
be afforded by the toes when they are closed in the forward motion of the feet. To pro- 
duce this effect, the inner of the three phalangeal heads of the bone is given off before the 
other two, and not by the side of them; but so far around on the inside of the meta- 
tarsus, towards its posterior aspect, that it lies almost directly beneath and behind the mid- 
dle head. On looking at the bone directly from before, this head is quite hidden from view. 
In consequence of this arrangement, the line of the articulation of the inner toe is very 
oblique, to enable the toe to be extended without interfering with the one next to it. 
The two other heads which form the distal extremity of the metatarsus, are placed side 
by side; the middle one being a little the larger and longer. They are very convex 
vertically, and each is marked with a median groove for the reception of corresponding 
median ridges on the heads of the phalanges. They are separated from each other by an 
exceedingly narrow but very deep furrow. 
Just above the inner head of the bone, on its interno-posterior edge, is a slight oval 
depression, on which rests the accessory metatarsal bone. This is a small, thin, flat, falci- 
form, almost unciform lamina of bone, entirely disconnected with the main bone, and simply 
applied loosely against it. It has no real articulation with the metatarsus; but its distal 
extremity is thickened for the support of the basal phalanx of the hallux.1 
1 I have recently been much interested in examining the 
very diverse modifications of this os metatarsale accessorium, 
both as regards its shape and its mode of connection with the 
metatarsus proper. To the end of ascertaining the amount 
of its variations in these respects, I have examined the halluces 
of many families and genera; in which labor I have been 
greatly assisted by my friend, Mr. A. E. Terrill, of Cambridge, 
Mass., who has taken the trouble to examine many forms 
which I had not at hand. The result of our observations 
shows that throughout the Natatores, and to a less extent 
among other Aquaticce, the bone deviates most remarkably 
from the ordinary type, as presented by the higher orders of 
Raptores, Insessores, Sfc. Instead of being very intimately con- 
nected with the metatarsus, or even more or less completely an- 
chylosed with it, and consequently immovable, and of a shape 
and general appeai’ance which unmistakably point to its true 
character, this metatarsal element becomes totally disconnected 
with the metatarsus except ligamentously, and is therefore 
quite loose and freely movable; in some instances there is a 
smooth articulating surface, which may not impossibly be even 
lined with synovial membrane, while a frequent elongated and 
cylindroid shape of the bone itself, joined with its other char- 
acteristics, gives it the appearance rather of a third phalangeal 
segment. 
very loosely connected with the metatarsus, and again present- 
ing the appearance of a third phalanx, it being half as long 
as the real basal phalanx. In the anomalous genus Rissa, 
usually described as “ tridactyle,” both this bone and the proper 
basal phalangeal segment, are present and quite distinct; the 
ungual segment being the deficient one. 
There is a remarkable peculiarity in the hallux of Puffinus, 
Thalassidroma, and probably most of the other genera of the 
large family Procellaridce. This is, that while the accessory 
metatarsal is present, the true basal phalanx is wanting. 
Professor Owen, indeed, says (Todd’s Cyclop., p. 288,) that 
“In the Petrel, however, this accessory metatarsal bone 
is wanting, although the hallux is present; the two bones of 
which, are therefore united to the principal metatarsal bone 
by long ligaments.” But, as suggested by Professor Wyman, 
it seems most rational that in such doubtful cases as the present, 
we should be guided in forming our opinions chiefly by the 
shape and position of the bone; and that, too, even if a cap- 
sule and synovial membrane exist, as is probably the case in 
Graculus. The bone in the genera now under consideration, 
has much the characters and general appearances which obtain 
throughout the allied family Laridce; which would seem to 
indicate correctly its real nature. 
It appears to be among the Totipalmi that the bone receives 
its most peculiar modification in size, shape, and connection. 
In Sula, Pelecanus, Graculus, &c., this metatarsal bone is 
nearly as long as the basal segment of the hallux, slightly 
curved, and of a cylindroid shape. Its proximal extremity has 
not the perfect articulating surface which its distal end bears; 
but nevertheless it is smooth, and nearly gives the impression 
of an articulating facet. Its character as a metatarsal element 
is "reatly over-balanced by Its phalangeal features, so that it 
is only by analogy that we can determine its proper place. 
Throughout the Laridce, this bone is found as a small, 
flattened, rounded, or irregularly polyhedral osseous nodule, 
The whole subject of the number of phalanges and their 
peculiarities in the class Aves, is an extremely interesting 
one, and well worthy of extended investigation. Since the 
announcement by Cuvier of the normal number of phalanges 
and of phalangeal segments among birds, the matter does not 
seem to have received the attention it merits, perhaps on ac- 
count of the well-known remarkable homogeneity of structure 
which obtains throughout the class. But lam of opinion that 
concerning this particular point there probably remain many 
anomalies, or at least peculiarities, yet to be brought into notice. 
Writers have not generally in their tables given, by any means, 
the whole number of the exceptions to the general rule, that are 
now well known to exist. 162 
COUES ON THE OSTEOLOGY 
Phalanges. The four toes possess the number of segments which normally exist through- 
out the vast majority of birds ; to wit, 2, 3, 4, 5, counting from the hallux to the outer toe. 
Some special features of each may be noticed. 
The hallux is of very moderate length, though comparatively longer than that of many 
other families of Natatores. Its two segments, together with the claw and accessory meta- 
tarsal, only measure one and a third inches. Its basal segment is long and very thin, and 
compressed ; its ungual is scarcely more than an osseous nodule for the support of the claw. 
Although this toe is not without its tendons, it appears to possess little motion, beyond 
what may be imparted to it by its membranous connections with the next one. It is fur- 
nished with a dependent lobe. 
The second toe is chiefly remarkable (besides its peculiar articulation with the meta- 
tarsus already noticed) for the great length of its basal segment, which considerably ex- 
ceeds that of the other two segments combined. 
All the phalanges of the middle toe are very stout and strong, much surpassing those of 
either the inner or outer toes in this respect. It is intermediate in length between the 
inner and outer toes. 
The outer toe is the longest of all. Its fourth segment, the penultimate one, presents 
the peculiarity of being considerably longer than either the second or third. 
The mechanism by which the toes are separated from each other, or abducted, at the 
same time that they are extended, forms an interesting feature in the feet of this and other 
birds. The metatarso-phalangeal articulation is a strict ginglymus, not admitting of lateral 
motion, nor of rotation. But the median grooves of the heads of the metatarsal bone, 
instead of running directly perpendicularly over the joint, are placed a little obliquely; 
i. e., that on the under head runs upwards and inwards; that on the middle head slightly 
outwards; that on the outer head is much more oblique. The planes of the heads of the 
metatarsus are also peculiarly twisted ; so that on their inferior aspects they all look to- 
wards each other; but as they mount upwards, gradually turn outwards or away from 
each other. Now the heads of the phalanges, when raised by the extensor tendons over the 
joint, follow the direction of these oblique planes, being guided by their median ridge which 
fits in the median sulcus in the metatarsal bone; and so, by the time they are fully ex- 
tended they also all look away from each other; and the webs are by this means spread. 
Thus the toes when extended must also be carried from each other; and they cannot be 
approximated except when flexed. The intention of this peculiarity is evident. The more 
forcibly the toes are pressed against the water the wider their webs are spread by the 
resulting separation of the toes; whereas if the toes could be approximated when in a 
state of extension, it would require constant effort to preserve the expansion of the webs. 
Myology. 
Cutaneous muscles. The principal of these is the large muscle which lies immediately 
beneath the skin of the neck and breast, so closely adherent to the skin as to be taken off 
with the latter in ordinary skinning. It has quite an extensive origin on the breast, ex- 
tending two or three inches on each side of the median line. The greater number of its 
fibres converge to pass up on each side of the median line of the neck, as narrow slips; 
but a thin, yet compact layer of longitudinal fibres completely encircles the neck, reaching 
quite to the occiput. OF COLYMBUS TORQUATUS. 
163 
A pair of musculo-tendinous slips arise by three separate digitations from near the 
extremities of the fifth, sixth, and seventh vertebral ribs; these digitations converge, and pass 
upwards and backwards to be inserted into the skin just over the apex of the scapula. 
These muscles are apparently offsets from the serrati magni. 
Another pair of musculo-tendinous slips pass to the skin, from the muscles just external 
to, and an inch below, the acetabula. 
Muscles of the Trunk. 
These need detain us but for a moment; their arrangement is as usual exceedingly 
complex, and probably presents no special peculiarities. It is only necessary, therefore, to 
notice the general features of the muscles of this region. 
The head of the bird is large and heavy, and its neck comparatively long. From the 
tip of the bill to the first rib, measures more than from the latter point to the end of the 
coccyx. In flying, as well as in diving and swimming under water, this ponderous head 
and neck are held straightly outstretched. To enable the bird to do this, and to execute 
the varied and extensive, as well as exceedingly rapid movements of the head and neck 
necessary to secure its living prey, the muscles acting upon these parts are well developed. 
Their general disposition is as follows : 
On the back the opisthotenar muscles commence about opposite the crests of the ilia, 
and extend along the fossae on each side of the spinous processes of the vertebrae. But 
as there is very slight mobility of this portion of the spine, the muscles are comparatively 
small and flat, and are moreover tendinous for a considerable portion of their extent. 
On the back of the neck, just anterior to the shoulders, where the greatest strain from 
the weight of the head and neck is experienced, the aggregate bulk of the muscles is ex- 
ceedingly extensive, much greater than at any other point along the spine. They are also 
almost wholly carneous, each of the numerous slips being muscular rather than tendinous, 
almost from their very origin. This is the point where the greatest mobility is required, 
as well as the greatest strength; and the two indications are fulfilled by the preponder- 
ance of the contractile over the non-contractile portions of the muscles, together with the 
increase in actual bulk of the muscular tissues. 
Passing along the neck toward the head the bulk of the muscles decreases, and they 
become more tendinous, to the middle, but from this point toward the head their size and 
fleshiness again increase, until near the occiput the aggregate volume of the complexus, 
trachelo-mastoideus, &c., amounts to nearly as large a mass as is found at the root of the 
neck. This is necessary for the adequate support of the large and heavy head. 
Biventer cervicis. The pair of muscles thus homologized by comparative anatomists, and 
which exists so constantly throughout the class, is very distinct in this species. Through- 
out their whole extent they receive no slips, and have no accessory attachments. They 
arise from the spines of the lowest cervical, or anterior dorsal vertebrae, as two slender 
round fleshy bellies; their central tendons are two or three inches long, after which the 
muscles again become fleshy, and as such are inserted side by side into the superior ex- 
tremity of the occipital spine. The muscular portion thus considerably exceeds the ten- 
dinous. 
The other individual muscles of the neck do not require special mention in this connec- 
tion. 164 
COUES ON THE OSTEOLOGY 
The muscles moving the caudal extremity of the spine, do not present any special 
peculiarities, with the exception of the cruro-coccygeus, or “femoro-coccygeus.” This, from its 
origin and relations, may be more conveniently considered in connection with the muscles 
of the posterior extremities. 
Of the abdominal muscles, the ohliquus externus vel descendens is particularly remarkable for 
its extensive origin, which causes it to form an investment, not only of the abdominal, but 
also of the greater part of the lateral thoracic parietes. It arises by broad aponeurotic 
digitations from the retrocedent processes of about seven ribs; from the margins of the 
ilium; from the horizontal ramus of the pubis; and from the posterior margin of the 
sternum, overlying a great part of the broad xiphoid cartilage; its fibres (as usual in the 
class) are directed inwards, with but a moderate inclination downwards; and continue 
carneous almost to the median raphfi, there being but a short aponeurosis before the inser- 
tion into the “ linea alba.” 
Muscles of the Upper Extremities. 
Pectomles. A remarkable peculiarity of the great pectorals is that they are united with 
each other by an extensive band of transverse fibres which pass across from one to the 
other just anterior to the keel of the sternum, lying upon the clavicular symphysis, and 
covering these bones for an inch or more. 
The fleshy mass commonly called the “pectoralis majorf consists of three portions, so 
very distinct from each other, in their origins and insertions, as well as in the motion they 
impress upon the humerus, that I prefer to consider them as distinct muscles. They are 
more distinct than the three glided of the human subject. 
The first pectoral, or “pectoralis maxinms,” is large, long, and broad, but very flat, and not 
thick. It arises from the whole of the clavicle; from the lower half of the fibrous septum 
which stretches vertically above it; from the side of the keel of the sternum (except that 
part occupied by the succeeding); and from the edge of the sternum all around, as high as 
the articulation of the last sternal rib. The mass laterally overlaps the edges of the bone; 
posteriorly is continuous with the fibres of the abdominal muscles. In the middle of the 
muscle is a broad longitudinal tendinous septum, which divides the mass into a greater por- 
tion, with origins as above, and a smaller part, which arises from an oblique ridge upon the 
face of the sternum. The fibres converge without twisting to the ordinary insertion. 
Pectoralis medius. Arises from the inner half of the anterior third of the keel of the ster- 
num (all that portion not occupied by the preceding); from the sternum itself as far as an 
oblique ridge which runs from the sterno-coracoid articulation to the keel, and separates 
this muscle from the next; and from the upper half of the supra-clavicular fascia. Its 
fibres converge to pass under a large trochlear surface of the coracoideum (converted into 
a foramen by the apposed clavicle) to their insertion by a stout rounded tendon into the 
ridge of the humerus near its extremity. 
It is a powerful external rotator of the humerus; and its further action elevates the 
humerus directly from the back, carrying its distal extremity in the arc of a vertical circle 
toward the head. 
Pectoralis minimus. Situated posterior and just external to the preceding, this muscle 
arises from the outer half of the broad base of the coracoideum, and the contiguous por- 
tions of the sternum. It is much smaller than the preceding, with the posterior border of OF COLYMBUS TORQUATUS. 
165 
which its anterior border is parallel and in apposition. It runs forwards and outwards, and 
is inserted directly into the internal tuberosity of the humerus. 
It adducts the humerus toward the body, and also depresses it when elevated. 
Latissimus dorsi. The two portions into which this muscle is divided are perfectly distinct 
as to their origin, direction, and insertion. The anterior portion is a narrow, thin, delicate, 
ribbon-like muscle, arising from the spines of about three vertebras opposite the middle of 
the scapula; passing directly outwards, over the scapular muscles, superficial to them all, it 
is inserted into the back part of the humerus, two inches below its head, opposite the inser- 
tion of the deltoid, close by the insertion of the posterior slip of the same muscle. 
The posterior division of this muscle, larger than the preceding, and broad and fan-shaped 
at its origin, arises from the last four or five dorsal vertebras ; its fibres rapidly converge, 
and it is inserted into the humerus close by the side of the preceding portion. 
These muscles draw the humerus directly backwards, slightly rotating it outwards. 
The scapula is connected with the spine by the two layers of muscular fibres, the 
trapezium and rhomhoideus, —as usual in the class. The fibres of the two planes decussate 
at right angles, in the ordinary method. 
The serratus magnus is very small and inconspicuous, arising by three digitations only, 
passing upwards and forwards, to its usual insertion into the apex of the scapula. 
Muscles of considerable size, the homologues of the teretes, infraspinatus and subscapidaris, 
proceed from the whole length of the scapula, below the origin of the extensor of the fore- 
arm to their insertion into the outer and posterior aspect of the head of the humerus. 
They rotate inward, and retroduct the humerus. 
The supraspinatus, smaller than the preceding, and quite distinct from them, arises from 
that portion of the scapula above the origin of the extensor cubiti; and passes as a rather 
broad and thin muscle, to be inserted into the back of the shaft of the humerus, one and a 
half inches below its head, by a thin tendon, fully an inch in breadth. It rotates the 
humerus slightly outwards, and directly retroducts it. 
Deltoid. Arises just at the coraco-clavicular articulation. It is small and weak, only 
about one and a half inches long ; it passes directly over the shoulder joint, to be inserted 
into the distal extremity of the external humeral crest. 
Immediately over the deltoid, and lying superimposed upon it, is the origin of the extensor 
plicce alaris. As this muscle passes over the most elevated portion of the humeral crest, it 
gives off a tendinous slip which is inserted into the crest, after which it passes on to its in 
sertion into the anti-brachium and metacarpus. 
Biceps flexor cubiti. This is rather a “biped” than a “biceps ” muscle; having apparently 
but one origin, and two insertions. It arises from the tip of the coracoid; passes as a 
rounded tendon along the depression between the anterior tuberosity and external oblique 
ridge of the humerus; continues single to the end of the first third of the humerus, where 
it divides into two fleshy bellies. The larger of these is inserted by a long round tendon 
into the tuber radii; the other seems lost in the fascia of the forearm; being also intimately 
blended with the fascia over which stretches the cutaneous fold at the bend of the elbow. 
A small muscle arises from the anterior aspect of the humerus, about half an inch above 
its condyles ; passing down mesiad of the tendon of the biceps, between it and the pronator 
radii teres, it is inserted into the inner border of the ulna, an inch or more from its head. 
This muscle lies more upon the forearm than upon the arm ; its whole action, however, is 
that of a flexor of the forearm; thus being perhaps analogous to the brachialis anticus. 166 
COUES ON THE OSTEOLOGY 
The triceps extensor of the forearm is divided into two perfectly distinct muscles, which 
may be called the “ long ” and “ short.” The former arises fleshy from the scapula half an 
inch below the glenoid fossa, passes as a stout, fusiform, fleshy belly to within an inch and a 
half of the olecranon, where it becomes tendinous; runs through a groove in the outer con- 
dyle of the humerus, to be inserted into the olecranon on its radial aspect. . About an inch 
from its origin it gives off a small but distinct flat tendinous slip, which passes obliquely 
upwards and backwards to be inserted into the humerus; it being joined by a similar slip 
given off by the latissimus dorsi, which is inserted with it. 
The other portion of the extensor is perfectly distinct, having a different origin and 
separate tendon of insertion. It arises from the posterior aspect of the shaft of the hume- 
rus for nearly its whole length; becomes tendinous near the elbow, and passing through a 
separate groove in the inner condyle, is inserted into the corresponding side of the olecra- 
non, just opposite the insertion of the longer extensor. 
Pronator radii teres ; Eupinator brevis. Arising respectively from the internal and external 
condyle, these two muscles converge towards their insertions into the radius exactly 
opposite each other. They directly antagonize each other; but, from the almost complete 
absence of pronation and supination in a bird’s antibrachium, probably act together, 
and thus serve to steady the radius. 
Extensor metacarpi radialis longior. As usual, a large muscle, the first one given off on 
the radial aspect of the limb. Arises high up on the external condyle by a flattened tendon, 
which soon changes to a fusiform fleshy belly; again changes, about the middle of the 
forearm, to a rounded tendon; this passes along a deep groove in the head of the radius, 
to be inserted into the radial aspect of the metacarpus. In its passage along the radial 
groove it is accompanied by the tendon of the next muscle. 
“ Extensor metacarpi radialis hrevior.” (Extensor proprius pollicis ?) This very slender 
small muscle arises from, and lies along, the ulnar aspect of the radius, its delicate tendon 
passing forwards along the radial groove with that of the preceding, to be inserted into 
the base of the pollex. Its tendon is more or less blended with that of the preceding; 
and any motion which it can impress upon the pollex must at best be but slight. It ap- 
pears to have rather the effect of an auxiliary extensor of the metacarpus, aiding the action 
of the preceding. 
A small, very slender, but long muscle arises from the internal condyle; lies along the 
ulnar aspect of the radius, beneath the preceding ; its delicate rounded tendon passes 
through a notch in the head of the ulna, and runs obliquely along the side of the meta- 
carpus ; divides into two slips, one of which goes to the base of the pollex, the other to 
the base of the first digit. This muscle adducts the thumb, and bends the metacarpus 
upon the anti-brachium. 
Flexor metacarpi radialis. Arises from nearly the whole length of the radial aspect of the 
ulna, and from the inferior aspect of that bone for its distal fourth. Its tendon passes ob- 
liquely over to the head of the radius; and is received into a deep groove, which carries it 
transversely across to the outer aspect of the wrist joint, where it dips deeply down to its 
insertion into the head of the metacarpus. This muscle seems to act as a flexor in the 
following interesting manner: When the hand is extended, or rather abducted, the head 
of the metacarpal bone, revolving in the radio-carpal articulation, carries with it the tendon, 
by which means the muscle is put upon the stretch. The contraction of the muscle, there- 
fore, will of course tend to restore the bone to its original position, and thus fold or adduct 
the pinion. OF COLYMBUS TORQUATUS. 
167 
Flexor carpi ulnaris. Of moderate size, fusiform shape, fleshy for nearly its whole extent; 
lying along the inner aspect of the ulna, its tendon inserted into the ulno-carpal bone, just 
in the angle of the wrist joint. It is a direct flexor or adductor of the metacarpus. 
The phalangeal flexors and extensors do not seem to require special notice. 
Muscles of the Lower Extremities. 
As might be expected from the peculiar formation of the bony framework of the lowrer 
extremities, and especially the shape of the pelvis, the muscles of this part of the bird 
present many interesting features, as regards size, shape, position, line of traction, etc. 
From the great length, and extreme narrowness and flatness of the pelvis, the muscles 
proceeding from it to the femur and tibia, or fibula, are of peculiar shape, and have fre- 
quently unusual actions upon the bones they move. Thus, the line of traction of the 
pubo-femoral muscles is such, that their action as femoral adductors is almost entirely lost, 
and they have become rather extensors of the thigh. Other muscles again, ordinarily flex- 
ors or extensors, seem to exert their chief action in producing the rotatory movements of 
the leg and foot upon the thigh which in this genus are so perfect and extensive. From 
the extreme tenuity of the sacrum, several muscles seem to take their origin from the 
spine itself rather than from the pelvis. From these peculiarities of position and action, 
I have found considerable difficulty in homologizing several of the muscles. I have gener- 
ally noticed them in the order in which they successively appear in the prosecution of the 
dissection. 
Sartorius. The first muscle given off to the lower extremities, arises apparently from 
the spine of the dorsal vertebra about opposite the apex of the scapula; passes down- 
wards and outwards at an angle of 45°, overlying the Missimus dor si, of a uniform width of 
about three fourths of an inch, to be inserted, by a flattened tendon, into the inner aspect 
of the projecting spine of the tibia, half an inch above the joint. It is fleshy throughout, ex- 
cept just at its origin and insertion. 
It is a powerful internal rotator of the leg; and to a less degree, an extensor. 
A broad, thin, fan-shaped muscle, the “ rectus femoris,” as homologized by most compara- 
tive anatomists, arises from the median line of the sacrum for a distance of four inches, 
commencing just below the origin of the preceding, with the lower border of which its 
upper border is parallel and in contact; lies superimposed upon the vasti, glutsei, and 
crurseus; its fibres pass directly outwards, converging from this extensive origin to a narrow 
flat tendon, which passes over the external condyle of the femur, to be inserted into the 
head of the fibula. The muscle is tendinous for an inch or more at its insertion, and just 
at its origin; otherwise fleshy. 
It is a perfect external rotator of the tibia, and therefore the antagonist of the preceding. 
From its insertion and the direction of its fibres it can have little or no effect as an ex- 
tensor. Its shape is such that with its fellow of the opposite side it forms a perfect trape- 
zium across the back of the pelvis. 
Biceps flexor cruris. A thin fan-shaped muscle, not unlike the preceding in shape, arises 
from the pelvis near the median line, from opposite the acetabulum as far down as the 
tuber ischii, being therefore partially overlapped by the preceding muscle. From this ex- 
tensive origin of about three inches, the fibres proceed directly outwards, converging to a 
flattened, then to a rounded, tendon. This tendon passes through a perfect fibrous loop, 168 
COUES ON THE OSTEOLOGY 
given off from the femur, (to be more particularly described hereafter,) by which its direc- 
tion is changed; now passing with a considerable degree of obliquity downwards, it is 
inserted into a tubercle on the outer aspect of the fibula, one and a half inches below the 
knee-joint. 
A direct and powerful flexor of the leg. In the passage of its tendon through the 
fibrous loop, and the consequent change in the direction of the line of traction, is seen a 
beautiful mechanism by which the force of the stroke as well as the extent of motion 
is increased when the backward movement of the leg is nearly completed; i. e., at the 
moment when the most vigorous impulse is requisite. This muscle is doubtless the biceps 
flexor, from its insertion and mode of action, though there is nothing at all bicipital in its 
shape. 
Glided. Filling the concave dorsum of the ilium, and lying close along the spine, is 
a mass of muscular tissue, which on its vertebral aspect is intimately blended with the 
spinal muscles proper, and with which some of its fibres appear superiorly continuous. 
I found it impossible to determine exactly the limits of the attachments of this muscle. 
It is incompletely divisible into two portions, which are however intimately united anteri- 
orly. The largest of these that nearest the spinal column passes backwards to be 
inserted into the great trochanter; the other lies nearly parallel, but its tendon is inserted 
further down on the outer and anterior aspect of the femur. 
The first of these muscles evidently rotates the femur inwards. The other is directly in 
the line of flexion; and though it cannot have much power, from its high insertion into 
the femur, it probably aids to flex, and somewhat inverts that bone. These muscles seem 
from their position and insertion, to be the glutceus medins and minimus, though from 
the peculiar shape of the parts, their actions are not identical with those of the human 
species. 
The muscle which probably represents the glutceus maximus is quite distinct from the 
others and smaller than either of them; and from the elongated shape of the pelvis, is 
entirely caudad of the femur, instead of lying in the same region and obliquely in the same 
plane with the other glutasi. It is a small flattish muscle, one and a half inches wide, lying 
close along the sacrum, on the pelvis, from an inch above the tuber ischii, to the femur. 
Its tendon runs forwards and obliquely outwards from the spine, to be inserted into a 
tubercle on the externo-posterior aspect of the femur, just below the trochanter, and just 
opposite the insertion of the above described glutceus minimus. The whole origin and infe- 
rior surface of the muscle is fleshy; but its tendon of insertion continues along its external 
surface to within an inch of its origin. 
As in the human species, this muscle extends and everts the thigh. It directly antago- 
nizes the glutceus minimus. 
OUurator. The obturator foramen is filled by a muscle which arises from its whole cir- 
cumference, lying between two layers of fascia. The small rounded tendon of this muscle 
runs forwards to be inserted into the posterior aspect of the great trochanter. It directly 
rotates the thigh outwards. 
Crurceus. A large muscular mass, lying upon the anterior aspect of the femur. Instead 
of converging to a tendon for its connection with the tibia, it has a very extensive muscular 
attachment to the posterior face of the whole length of the tibial spine that projects above 
the knee-joint. 
This is the direct extensor of the leg. Although so short, only as long as the short OF COLYMBUS TORQUATUS. 
169 
femur, yet its action must be powerful, from the amount of contractile fibre it contains 
and from the great increase of leverage obtained from the projecting spine of the tibia. 
Vasii? On either side of the preceding lies a smaller muscle, having its origin from 
the femur near its head. They proceed over the femoral condyles to be inserted respec- 
tively into the inner side of the head of the tibia, and into the head of the fibula close to 
the articulating surface. 
From the origin and position of these muscles, they seem to represent the vasti; but by 
a slight variation in their insertion, their function is entirely changed. They can exert 
but very slight, if any, action as extensors of the leg. They are rotators of the leg 
upon the thigh. The internal one acts conjointly with the sartorius; while the external 
one is intimately blended with the tendon of the broad fan-shaped muscle, above described, 
and referred to the rectus femoris. 
It will thus be seen, that of the four muscles which in the human species conjoin to form 
a “ quadriceps extensor cruris,” only one, the crurasus, is here left as a proper extensor. The 
rectus joins the vastus externus, and both are together inserted into the head of the fibula, 
to act rather as external rotators; while the vastus internus forms an internal rotator, in 
which action it is assisted by the sartorius. 
The “ pubo-femoral ” muscles, the proper adductors of the thigh, are represented by 
a broad plane of muscular fibre, which arises from the whole length of the horizontal ramus 
of the pubes, and from a considerable portion of the obturator fascia. From this extensive 
origin the muscle converges as a thin flat plane, to be inserted by a broad tendon into the 
lower half of the femur. I was not able to divide these fibres into distinct muscles. 
A large, somewhat flattened muscle arises from near the tuber ischii, and from the sides 
of the sacrum nearly as far as the femur; also from the surface of the pelvis not occupied 
by the glutmus maximus, which it overlies, and proceeds obliquely upwards and outwards, 
to be inserted into a tubercle on the inner and posterior aspect of the femur, a little below 
its middle. On the external surface, the tendinous portion of the muscle extends to within 
two inches of its origin; but on the internal aspect the muscle is fleshy, nearly to its point 
of insertion. 
The first of the two preceding muscles is of course homologous with our adductors, 
and the latter would seem from its insertion to belong to the same class. But however 
this may be, the shape of the pelvis, and the relative position of the femur are such, that 
any action they may have as adductors can be but slight, and must be greatly overbal- 
anced by their more energetic action as extensores femoris. 
In connection with the muscle last described, there is to be noticed one belonging to 
quite a different set, viz. the “femoro-coccygeair This is a small, narrow, ribbon-like muscle 
arising from the base of the coccygeal vomer. It proceeds forwards, fleshy, for two and a 
half inches, changes suddenly to a small rounded tendon, which lies along the outside of 
the tendon of the muscle last described. They soon become intimately blended together, 
and proceed as one tendon to their insertion into the femur. 
There is thus a strong “ guy ” proceeding on each side of the pelvis from the femur to 
the coccyx, reminding one irresistibly of the tiller-ropes of a boat’s rudder. Acting to- 
gether they serve to steady the tail; more strongly contracting, they draw it downwards; 
while either acting alone draws the tail obliquely downwards and to the corresponding 
side. 
Semi-tendinosus. Arises from the tuber ischii, being at its origin intimately blended with 170 
COUES ON THE OSTEOLOGY 
the second of the two femoral “ adductors ” just described. It crosses obliquely over the 
coccygeal muscle; passes outwards and forwards, and is inserted by a narrow flat tendon 
into the tibia, about an inch below the joint. 
Semwnembranosus. Arises from the pelvis about midway between the acetabulum and 
tuber ischii, and is inserted by a broad membranous tendon into the crest of the tibia just 
above the insertion of the preceding. It is a thin flat muscle, with a tendon fully as wide 
as the fleshy portion. 
These two muscles are the proper flexors of the leg upon the thigh. Their tendons 
form the “ inner hamstrings,’’ and from their situations, relations, and uses are undoubtedly 
to be homologized with the semi-tendinosus and semi-membranosus. 
In my dissections I failed to detect a “gracilis” muscle; or any connection of a tendon 
of a crural extensor with a digital flexor, by which flexion of the toes is produced by the 
mere bending the knee and ankle-joints, as is the case with the Insessores, etc. Ido not 
think that such a mechanism exists, at least to any marked degree, although I may be 
mistaken. 
Considering collectively the muscles which act upon the thigh and leg, it will be noticed 
that by far the greater part of their combined force is exerted to produce powerful extension 
of the thigh and flexion of the leg, with a free rotation of the latter upon the former; while 
the power of flexion of the thigh, and extension of the leg, is reduced in a proportionate 
degree. The importance of such a disposition of the muscular forces of the parts to the 
full development of vigorous natatorial power, is too evident to need comment; for the 
bringing forward of the leg requires but very slight effort in comparison with that neces- 
sary to produce the energetic backward stroke by which the bird is propelled forward. 
Now, in examining the muscles of the leg and foot, we shall find that they are so disposed 
as to most effectively continue the powerful backward stroke which began at the hip-joint. 
The extensors of the metatarsus vastly predominate both in number and size over the 
flexors. No less than seven tendons pass over the posterior aspect of the tibio-tarsal 
articulation, while only three are found upon its anterior face. I will notice the more im- 
portant of these muscles. 
Tibialis anticns. Arising from the very tip of the projecting spine of the tibia, and from 
the whole anterior aspect of that spine down to the joint, it lies along the face of the bone 
for its whole extent, though no more fibres take origin from it. It is fusiform in shape. 
Its tendon passes directly over the anterior surface of the joint, being bound down by a 
transverse ligament, and is inserted into the head of the metatarsal bone. It directly 
flexes the tarsus. 
Extensor digitorum communis. Much smaller than the last, lying beneath and internally to 
it. It is somewhat penniform in shape, its tendon running up for some distance on its 
inner edge, its outer surface being covered with dense fascim. It arises from the anterior 
aspect of the spine of the tibia, down as far as the knee-joint, for which extent it is inti- 
mately blended with the muscles by which it is surrounded. After passing the joint, it be- 
comes distinct from any other muscle; but fibres continue to take origin from the face of 
the tibia for nearly its whole length. Its tendon passes behind and internal to that of the 
tibialis anticus, passes through an osseous canal formed by the bony bridge which stretches 
across between the malleoli, and runs along the anterior edge of the metatarsal bone, in a 
deep sulcus; about half an inch from the end of the bone, it gives off the tendon which 
goes to the inner anterior toe; this at once divaricates in a special groove, while the tendon OF COLYMBUS TORQUATUS. 
171 
proceeds to the head of the metatarsal bone, just over which it splits into two for the mid- 
dle and outer toes. The tendons extend to the bases of the last phalanges on each toe. 
Peroneus. Much smaller than either of the others, this muscle arises from the fibula for 
the greater part of its length. Its tendon passes through a separate canal in the annular 
ligament, on the outer aspect of the joint, and proceeds obliquely backwards, to be inserted 
into the posterior border of the metatarsal bone, just at its base. From the peculiar posi- 
tion of the tendon where it is bound down, as well as by its insertion, it can have little or 
no effect in moving the tarsus backwards or forwards. When the tarsus is extended it may 
weakly aid in extending it; but its principal office is evidently to direct and restrict the 
rotatory movements of the tibio-tarsal joint. It quite powerfully rotates it outwards, and 
antagonizes the tibialis posticus on the outer side of the joint. 
Gastrocnemii. In the gastrocnemii there is seen the same plan as was noticed in the 
“ triceps''1 extensor cuhiti, viz. a tendency to divide into two distinct muscles. It is not, 
however, so strongly pronounced as in the former instance, though the three origins of the 
gastrocnemius are even more wudely diverse. 
The inner, or rather the anterior gastrocnemius lies upon the inner and anterior aspect of 
the tibia for its upper two thirds, afterwards crossing the leg obliquely, to get upon its pos- 
terior aspect. It has two heads; one arising fleshy from the apex of the tibia! spine, from 
the whole anterior face of the upper two thirds of the bone, and from the fibrous septa 
between it and other muscles; the other from the inner condyle of the femur; the ten- 
dons of the semi-tendinosus and semimembranosus being interposed between them. 
The posterior or outer gastrocnemius arises from the “ tinea aspera ” for nearly two thirds 
its length, and from the outer condyle ; also receiving attachments from the muscle 
described as the rectus femoris. 
These two portions of the muscle, thus diversely arising are fleshy to within two inches 
of the heel. There they change into two stout round tendons, entirely separate from 
each other. A little above their final insertion they fuse into one broad, thick, very power- 
ful tendon, which passes directly over the posterior aspect of the joint, (overriding the 
tendons of the other muscles,) and is inserted into the base of the bony protuberance on 
the back of the metatarsus. 
At the mesial edge of the insertion of the last described portion of the gastrocnemii, 
there proceeds down from the femur a most perfect sample of an aponeurotic loop. This 
loop encircles the tendon of the biceps flexor cruris, and changes the direction of its line of 
traction as much as does the loop which in our species binds down the tendon of the 
digastricus to the hyoid bone. It runs down from the femur as a distinct narrow fibrous 
band; embraces the tendon, and returns upon itself, the two ends of the loop being in- 
serted side by side. This loop is more or less blended with the fibrous investment of the 
under surface of the gastrocnemius. 
The dissection and examination of the remaining muscles of the back of the leg is ex- 
ceedingly difficult. They are all more or less intimately united with each other, throughout 
the greater part of their muscular as well as tendinous structure. They arise from the outer 
and posterior aspects of the bone, and from the intermuscular septa between one another. 
They become tendinous at very various points. Their tendons, however, are all aggregated 
together to pass directly over the posterior aspect of the heel. Just over the joint, nearly 
all are enclosed in one large dense shiny white mass of fibro-cartilage, through which each 
tendon bores a canal for itself. Leaving this sheath, all but one (the tibialis posticus ?) 
11 172 
COUES ON THE OSTEOLOGY OF COLYMBUS TORQUATUS. 
pass through the canals of the bony protuberance which is sujDerimposed upon the base of 
the metatarsal bone, and proceed to their different digital insertions. This bony canal is 
subdivided by osseo-cartilaginous septa into three divisions : a quite large central posterior 
one, through which the majority of the tendons pass; and two or three smaller latero- 
anterior ones, for special tendons. I will notice two of these muscles which are quite 
distinct as to their insertions, and consider the others collectively as the digital flexors. 
Tibialis posticus ? A muscle which I thus doubtfully homologize, not from its position, 
but from its insertion and evident action, arises from the very apex of the tibial spine, and 
from the fibrous septa between it and contiguous muscles. Its tendon passes with the 
others through the fibro-cartilaginous envelope; but then divaricates, to be inserted into 
the inner aspect of the base of the metatarsal bone. It is the evident antagonist of the 
peroneus already described; directing and limiting the rotation of the tarsus. 
The inner anterior toe has a special flexor of considerable size. Its tendon passes over 
the back of the joint, through one of the smaller divisions of the bony canal; and proceeds 
to its insertion along a deep groove on the posterior edge of the metatarsal bone. 
The common flexors of the digits as usual consist essentially of two sets, a perforans and per- 
foratus, though the expressions “ superficial ” and “ profound ” do not here hold good, as 
they have no such relative position. The tendons of the two sets, however, do really lie 
superimposed upon each other, and the one divides for the passage of the other, much as 
in the human species. The interlacing of the tendons of the different flexors is exceedingly 
intricate. Almost every one sends tendinous slips to one or more of the others; so that 
the most simultaneous action of all the toes is secured; and though the fleshy bellies of 
some of the tendons have diverse origins, the combined effect of the whole seems to be 
that of a single powerful flexor. 
Explanation of Plate V. 
Fig. ]. Superior aspect of skull. 
Fig. 2. Lateral aspect of skull. 
Fig. 3. Inferior aspect of skull. 
Figs. 1, 3, are without the inferior maxillary. These three figures are of the natural size. 
Fig. 4. Pelvis and posterior extremities in situ. One half the natural size. 
Published November, 1866. Memoirs Boston So c. IST a t.Hist.Vol. 1. 
Plate 5. 
Cones on the Osteology of Colymbns torquatus. 
A.Meisel Li Eh.