176 BULLETIN NO. VII. 
GENUS VESPERIMUS, Cougs. 
A word of explanation is necessary in thus employing the 
name usually considered subgeneric under Hesperomys as of full 
generic value. This change was the result of an attempt to 
diagnose the genus Hesperomys as it now stands in ‘our litera- 
ture, with the groups Vesperimus, Onychomys, Oryzomys, Calomys, 
Habrothrix and Oxymicterus as subgenera. It was found impos- 
sible to distinguish these genera collectively from the associated 
genera by any characters of a higher sort than those separating 
them among themselves. In this dilemma the simplest remedy 
seemed to be to disregard altogether the generic name 
Hesperomys, which was,as pointed out by Baird, orginally applied 
, to the whole group of Siymodont Muride. Moreover, Hesperomys 
would need to give place to the prior name, Sigmodon, if its sig- 
nification were simply restricted to the whole group to which 
it could naturally be applied. _ Sigmodon, however, is duly rec- 
ognized as a valid generic term, and for our part we do not see 
that any harm can result from the change proposed. 
The genus Vesperimus was amply characterized by its founder 
and, as by him diagnosed, includes animals of medium or small 
size, lithe form and quick movement. The long hind legs and 
rather short anterior extremities adapt them for rapid running 
and springing, while the short fore claws indicate that they are 
not fossorial. The fore feet are rather less than half as long 
as the six tubercled soles. The palms are naked, while the 
soles, in most of the species, are furry posteriorly. The tail is 
usually long as compared to other native mice, ranging from 
considerably longer than the remainder of the body to the’ 
length of the trunk alone. 
The head presents an animated appearance. The bright 
prominent eyes, large sparsely pilous ears and acute muzzle 
conspiring to give vivacity to the face. The ears are unusually 
large and thin. The colors are bright, and the contrast between 
the upper and lower surfaces of both body and tail is marked. 
The most unreflecting person would be forced to admire the 
sprightly deer mice, and they universally attract attention, 
while their inroads upon the graneries are rarely so great as 
to merit the execration poured upon their domestic cousins. 
The cranial and other anatomical characters may be gathered 
from the specific description beyond ; a few points only need 
be noticed. Characteristic features are the slender rostral 
part occasioned by development of the nasals and premaxilla- 
ries, the broad, low, cranial portion, and deflected zygomas. 
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