’"PROCEED!?? ns "DF ST.O'ES NATIONAL MUSEUM. 
DESCRIPTION OF HESPEROMYS TRUEI, A NEW SPECIES BELONG- 
ING TO THE SUBFAMILY MURINiE. 
B. W. SIIU1?EI.1>T, 77. S. Army. 
Fort Wingate is a military station about 3 miles off the railroad in 
northwestern New Mexico. The country about it is hilly, with broad 
and more or less level valleys dividing the broken ranges. These hills 
support a growth of low pinons and a species of scrub-oak, while in 
many places their sides are covered with irregular groups of loose 
boulders of sandstone rock. 
The highest point is something between 7,000 and 8,000 feet above 
the datum plane. The midsummer days may be very warm, and the 
thermometer has been known to fall as low as 15° Fahr. below zero in 
the winter months. 
Among the smaller mammals to be found in this locality, the south- 
western form of Neotoma floridana is probably the most abundant. 
This handsome little rat often constructs its nest beneath one of the 
uptilted boulders, or sometimes in a fissure between two of them, and 
structures of this kind are frequently to be noticed in such situations 
as we ramble over the hill-sides, where the smaller masses of rocks are to 
be found. Occasionally it chooses for its home the shelter afforded by 
the gnarled roots of a pinon, where the elements have forced them above 
ground, or, more rarely, the hollow trunk of one of these trees, should 
it occur in a favorable situation. 
Until the 16th of March, 1885, during my collecting excursions 
about Fort Wingate, I never experienced any difficulty in capturing, 
whenever I chose, a few specimens of this rat. All one had to do was 
to simply tear open one of their nests and pounce on its inhabitant with 
gloved hands. After the date mentioned, however, they suddenly dis- 
appeared, and on that very day I opened seven of these nests, appar- 
ently all new ones, only to find in each instance the owner missing. 
On my way home from this unsuccessful hunt my attention was at- 
tracted to the outer covering of another nest protruding from an open- 
ing in the dead and hollow trunk of a small pinon, at least 2 feet 
above the ground. This was an uncommon site for the nest of a Neo- 
toma, and taken in connection with the absence of the usual pile of rub- 
bish about the entrance, and the small size of the trunk chosen, my 
curiosity was sufficiently aroused to determine me to investigate the 
occupant’s stronghold. 
The nest, composed of the fine fibers of the inner bark of the pinon, 
was soon pulled out, and its owner dislodged and captured alive and 
unhurt. It proved to be a mouse about half the size of the average 
Neotoma, colored very much like one, but possessing a pair of ears that 404 
PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
[1885. 
immediately impressed me on account of their being so disproportion- 
ately large for an animal of its dimensions. 
For two days I kept this engaging little creature alive in my study 
for the purpose of making a drawing of its head and studies of its be- 
havior and attitudes. It was then killed, carefully measured, skinned, 
and skeletonized. 
A. glance at its skull was sufficient to remove from my mind the last 
of any doubt I may have entertained as to its being a half-grown wood- 
rat. Indeed, its extraordinary ears had already fairly satisfied me of 
this fact, as they were fully as large, or even larger, than the average 
size of those appendages in the Neotoma. Besides, it was the wrong 
time of the year to come across a young animal of that species, to say 
nothing of the general appearance of maturity it evidenced both exter- 
nally and in its skeleton. 
Concluding, then, that it was some variety of Hesperomys, I forwarded 
the skin to my friend Mr. F. W. True, curator of the department ot 
mammals in the United States National Museum. In his courteous and 
prompt reply he gave me to understand that he believed it to be “a 
typical H. leucopus, except so far as its ears are concerned.” The diag- 
nosis of course could not be conclusive, as he had not seen the skull of 
my specimen, and even the ears had somewhat shrunken in the skin, 
as they are sure to do. 
Here the matter rested until the 16th of May, just two months after 
the capture of the specimen in question. On this date I was engaged 
in hunting for insects, not a thousand yards from the tree on the hill- 
side where my first specimen of Hesperomys was taken, but this time 
out in the broad valley that stretches between the latter point and the 
opposite range of hills. In turning over a heavy plank I surprised a 
family of field mice, but encumbered as I was with my collecting case 
and gun, I succeeded in capturing only the male and three half-grown 
young; the female and four more of the young ones making good their 
escape. The young proved to be about half the size of their parents, 
and of a deep slate color, forming a striking contrast with the light dun 
color of the latter. 
Naturally, the first thing I examined in my new captive were his ears; 
these I found to be of like proportions with the same parts, as I remem- 
bered them, in eastern forms of field mice. These four specimens were 
consigned to alcohol for future comparisons with such other material as 
might come to hand. 
Being convinced now that my first capture was a new species, I forth- 
with communicated with Mr. True to ascertain what could be done in 
regard to exact identification and description, as I was desirous of hav- 
ing the proper material before me for comparison. 
Through this gentleman’s kindness I was delighted to have at my 
command at the end of the following fortnight the subjoined list of ad- 
ditional specimens to compare with those already in my possession: 1885.] 
PROCEEDINGS OF UNITED STAT1 S NATIONAL MUSEUM. 
405 
Specimens. 
Locality. 
Donor. 
Catalogue 
number. 
Eemarks. 
1. H. leucopus 
Fort Simpson 
Middleboro’, Mass 
B. E. Eoss 
4520 
Skin. 
1. H leucopus 
J . W. I1. Jenks 
1434 
Skin. Flat. Mus. typo. 
1. II. leucopus — 
1. H. leucopus 
1. II. leucopus 
9251 
Skin. 
7183 
Skin. 
Pennsylvania 
Dr. E. Michener 
4856 
Skull. 
1. II. leucopus, 
Missouri 
Dr. F. V. Hayden 
2235 
Skull. 
Fortunately ou the 30th of the next month, and in the same valley 
where I had taken my male and three young, another capture was made, 
this time a female of the little harvest mouse, Ochetodon humilis, with 
three young barely an hour old. These latter were placed in alcohol, while 
the mother was carefully measured, skinned, and skeletonized.! The 
measurements will be found in the comparative tables below. 
Along with the specimens from the National Museum, Mr. True also 
sent me Coues’s measurements and identifications of the same. These 
former are in inches and fractions, and as I employ in making such 
measurements the metric system only, I have carefully reduced Coues’s 
measurements in the table to that scale, in order to conveniently com- 
pare them with my own, as taken from three of my Fort Wingate cap- 
tures, referred to in the foregoing paragraphs. 
Table of measurements of six skins of Hesperomys, including the type of H. Trued ; and of 
one skin of Ochetodon humilis. 
[Taken in centimeters and fractions.] 
Nose to— 
Tail to— 
A 
o 
Specimens. 
© 
u 
"S 
© 
d 
a 
«M 
o 
o 
8 
1 
© 
o 
*c5 
O 
Soles. 
rtf 
© 
© 
■3 
© 
Pi 
c§ 
© 
O 
fc 
Remarks. 
W 
w 
o 
« 
w 
« 
Q 
w 
4520. Hesper- 
omys leucopus, 
?■* 
1434. Hesper- 
omys 1 e u c o - 
pus.* 
9251. H. 1. sonori- 
ensis.* 
7183. H. leuco- 
pus.' 
1. 5 
2.0 
3.8 
7.7 
7.3 
7.6 
1.9 
1.7 
1.3 
1. 3 
2. 5 
3.0 
8. 9 
8.1 
8.4 
1. 3 
Nat. Mus. type. 
Skin stretched. 
1. 4 
2.4 
3. 2 
8. 7 
1. 6 
1.3 
2. 3 
3.0 
7.6 
1.3 
Manus. 
Pes. 
14904. Hesper- 
omys Truei, cf • 
1.3 
2.4 
3.5 
8.7 
8.2 
9.2 
1.0 
2.0 
2.5 
Collected at 
Fort Win- 
gate, N. Mex., 
16 March, 
1885, by Dr. 
R. W. Shu- 
feldt, U. S. A. 
*1 have taken the liberty to add a few measurements to those taken hy Coues, and correct others. 
t It may be of interest to remark here that of the many specimens of the south- 
western types of Neotoma floridana that I have taken and measured, the females have 
always proved to be notably larger than the males.—R. W. S. 406 
PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
[1885. 
Table of measurements of six skins of Hesperomys, 4'C.—Continued. 
Nose to— 
Tail to— 
rd 
o 
Specimens. 
+3 
‘Ss 
CM 
o 
82 
u 
a? 
1 
«m 
£ 
*3 
«M 
Soles. 
o 
P4 
# 
© 
© 
© 
Cm 
O 
A 
© 
«m 
C 
Remarks. 
Eye. 
c3 
P 
P4 
O 
© 
O 
-M 
O 
o 
P 
a 
P 
3 
P 
Manus. 
Pes. 
-m 
P4 
© 
P 
b£ 
*© 
w 
Hesperomys leu- 
copus, cf- 
1.4 
2.4 
3.1 
7.8 
7.2 
7.5 
1.1 
2.0 
1.7 
Collected at 
Fort Win- 
gate, N. Mex., 
16 May. 1885, 
by Dr. R. W. 
Shufeldt, U. 
S. A. 
15130. Ochetodon 
liumilis, $. 
i 
1.1 
2.1 
2.4 
7.1 
6.1 
6.3 
0.9 
1.6 
1.3 
Collected at 
Fort Win- 
gate, N. Mex., 
30 June, 1885, 
by Dr. R. W. 
Shufeldt, U. 
S. A. Nurs- 
ing three 
young when 
captured. 
Other interesting measurements are to be obtained from the two skulls 
of Hesperomys leucopus and that of Ochetodon humilis now before me, 
and for their convenient comparison these are also presented in a tab- 
ulated form. 
Table of measuremen ts of three skulls of Hesperomys, including the type of H. Truei, and 
of one skull of Ochetodon humilis. 
[Given in centimeters and fractions.] 
Catalogue number. 
Species. 
M 
<V 
in 
Greatest length of 
skull. 
Interzygomatic di- 
ameter (greatest 
width). 
Depth of skull meas- 
ured from vault of 
cranium to basi- 
sphenoid. 
Remarks. 
2235 
Hesperomys sonoriensis 
* 
2.55 
1.45 
0.8 
ffff d Nat. Mus. collection, 
Lower Missouri. 
4856 
H. leucopus 
2.55 
1.20 
0.8 
4856 Nat. Mus. collection, 
Pennsylvania. 
14904 
H. Truei 
<5 
2.90 
1.50 
0.9 
Collected by Dr. Shufeldt. 
From specimen in preced- 
ing table. 
15130 
Oclietodon humilis 
? 
2.10 
1. 05 
0.7 
From last specimen in pre- 
ceding table. Fort Win- 
gate, N. Mexico. 
It is evident, aside front other characters given below, that the 
extraordinary size of the ears of the mouse captured by me on the ICth 
of March, as well as the superior dimensions and varying ratios of the 
diameters of its skull, entitle it at least to distinction as a new species. 
It gives me pleasure, therefore, to bestow upon it the name of my es- 
teemed friend Mr. F. W. True, curator of mammals, in the United States 
National Museum. 1885.] 
PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
407 
All of the specimens of Hesperomys loaned me for comparison by the 
National Museum have the upper parts of a bright yellowisli-brown, 
inclining to a tan color, while the parts beneath are of a pure white, 
the line of demarcation between the two being very distinct. Now, 
all the specimens of Hesperomys from this region are of a very pale, dull 
clay color above, and white beneath, but the line of demarcation not so 
evident at first sight, in consequence. 
The dental formula in True’s mouse agrees with the Murinee generally, 
being, incisors § and molars |D-|; we notice, however, in the specimen 
that the cusps of both the mandibular and upper molars have been en- 
tirely worn off', leaving a shallow, longitudinal groove along their upper 
surfaces, connecting the three crowns. I am unable to say at the present 
writing what this is due to, or how constant it may be. To decide this 
we must have a better knowledge of the character of the food of this 
mouse, as well as the opportunity to examine specimens of different ages. 
H. leucopus of this region, inhabiting as it does the valleys, no doubt 
subsists upon the softer vegetable substances which give rise to but 
little abrasion of the molar teeth, whereas H. Truei, a species which 
has chosen the rocky mountain sides for its home, now lives upon the 
flinty pinon nuts, and the spiny leaves of the trees upon which they 
grow, and these substances may have something to do with the wear- 
ing down of the molar teeth. The implantation of their roots agrees in 
general with that observed in other members of the genus, and these 
uon-visible parts are equally well developed in them. 
In the mandible of Hesperomys, we find the condyle and the small 
corouoid process separated by a long, shallow, longitudinal valley 
(Figs. 7 and 8, pi. XXI). 
Again, in Hesperomys the nasal processes of the maxillaries do not 
project behind the nasals, as they invariably do in Neotoma (Figs. 4 
and 5, pi. XXI, N. Mx., N. Mx'.). It is of interest to know also in re- 
gard to these two genera, that the ratios of the longitudinal and trans- 
verse diameters of the interparietal bones differ very markedly. 
Hesperomys Truei, sp. nov. 
True’s Pinon Mouse. 
DESCRIPTION. 
(Adult male, in the flesh.) 
A Hesperomys with a form more robust than in most others of the 
genus. Eyes large and capable of extraordinary protrusion when the 
animal is affrighted. Whiskers very long and many-haired. Ears pre- 
senting the normal generic characters, but remarkable for their unusual 
size. Upper halves are delicate, thin, and very sparsely covered with 
shoi t, fine hairs. Fur rather longer than common, soft, loose, and flossy. 
Tail more thickly haired than in H. leucopus, and the hairs longer. 
Color.—Upper parts of a yellowish brown with an admixture of blaek- PKOCEEDINGS OF IGNITED STATES NATIONAL MUSEUM. 
[1885. 
isli hairs, the latter best marked on the dorsum, becoming less so as we 
approach the sides. Sides bright fulvous. Entire under parts white, 
blending with the fulvous of the sides, the line of demarcation being 
by no means so evident as fn H. leucopus. Upper sides of feet white. 
Tail bicolor; upper side blackish brown, white beneath. Manus and 
pes agree with H. leucopus. 
Dental characters.—In the dental formula, as well as the method of 
implantation of the teeth, this animal agrees with H. leucopus, but in 
this, the type specimen, the crowns of the molars are peculiarly worn 
away, as described above. It will be interesting to examine other spec- 
imens with the view of looking into this subject, ascertaining, if possi- 
ble, how far this condition is constant, and to what extent it may be 
due to age. 
Cranial characters.—Although the skull presents in general the char- 
acters of the genus, it is considerably longer and larger in other ways 
than the skull of H. leucopus. (Sec table.) This increase in size has 
not been accompanied by an increase of strength or thickness of this 
structure; on the other hand, if anything, the skull of True’s mouse is 
of a more attenuated and delicate composition than that of the com- 
mon white-footed mouse. The basi-occipital is more emarginate also 
than in that species, and the periotic is quite different in form. 
In the mandjble we find that the symphysial portion is not bent up 
so abruptly as it is in all forms of H. leucopus, and in cousequence the 
lower incisors are directed about equally forwards and upwards, while 
in H. leucopus these teeth are, in most specimens, curved almost en- 
tirely upwards. (Figs. 7 and 8, pi. XXI.) 
The skeleton of H. Truei presents many characters, apparently of 
specific value, by which it may be distinguished from that of H. leuco- 
pus. The manubrium of the sternum is shorter in the former species 
than in the latter; the anterior margin of the scapula is larger and 
more sharply angulated, and the posterior margin straigliter; the pos- 
terior margin of the pelvis is much more rounded; the transverse proc- 
esses of the lumbar vertebrae are more slender, and those of the sacrals 
wider. 
True’s pinon mouse differs then from the common white-footed mouse, 
H. leucopus, in the fact that it chooses a different character of the 
country where it is found, as its home; in its more robust form ; in its 
extraordinarily large ears ; in important cranial and skeletal characters; 
and in a very marked degree in general coloration, though less weight 
is to be attached to this last difference than to any of the others. 
At present little or nothing is known of the habits of this mouse; 
in these, however, it probably largely agrees with other field mice. 
Living in the mountainous and pinon-covered belts of this region; 
building its nest in the hollow trunks of trees; subsisting upon such 
food as the country would afford a small rodent, and hibernating dur- 
ing the winter months. Proceedings Nat. Mus., Vol. YUI, 1885.—Shufeldt. 
PLATE XXI. 
Jig. Z. 
Jig. 3. 
Fig.l. 
Tig- 7- 
Tig. 8. 
Fig. 4. 
TiS- 
Fig- #• PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
[1885. 
EXPLANATION OF PLATE XXI. 
Fig. 1. Head of Besperomys Truei, $, life size. From the specimen captured at Fort 
Wingate, N. Mex., March 16, 1885. 
Fig. 2. Head of Besperomys leucopus sonoriensis, , life size. From the specimen 
taken at Fort Wingate, N. Mex., May 16, 1885. 
Fig. S. Head of Ochetodon humilis, 9 , life size. From the specimen taken at Fort 
Wingate, N. Mex., June 30, 1885. 
Fig. 4. Superior aspect of the cranium of Neotoma floridana, $, natural size. Speci- 
men taken at Fort Wingate, N. Mex., January 11, 1885. 
n. mx. Nasal process of the superior maxilla. 
Fig. 5. Superior aspect of the cranium of Besperomys Truei, $ , natural size. Type 
specimen. 
n. mx'. Nasal process of the superior maxilla. 
Fig. 6. Left lateral view of mandible of Neotoma floridana, natural size. Same 
specimen as Fig. 4. # 
Fig. 7. Left lateral view of mandible of Besperomys leucopus, natural size. Speci- 
men 4856, National Museum Collection. 
Fig. 8. Left lateral view of mandible of Besperomys Truei, natural size. Same 
specimen as Fig. 5. 
(All the figures drawn from nature by the author.)