RODENTIA—GEOMYINAE—THOMOMYS UMBRINUS. 401 
The specimens No. 154, 149, agree very well with-each other, the colors of the latter and 
smaller one being brightest. 
A specimen (611) collected by Dr. Henry, probably at the Copper Mines, agrees in all essential 
characters, except that the furrow of the incisors is a little more distinct, and the reddish of 
the under parts is a little more mixed with paler. Another of much larger size, (612,) appears 
bleached ; the under parts being much paler than as above described. The body measures 
nearly eight inches. The tail is, unfortunately, mutilated, by having been broken off near the 
base ; the wound is, however, cicatrized. This mutilation of the tail is very common among 
the species of Geomys, rendering it difficult to apply the proportional length of this member as 
a specific character. It is probable that this result is produced in the course of the contests in 
which male mammals periodically indulge. 
This species, in general appearance, has a close resemblance to 7. bulbivorus, from the Pacific 
coast, though a careful comparison shows many points of difference, which, though slight, are 
as characteristic as generally prevails in this group. The claws are uniformly longer, stouter, 
and considerably more curved. The toes, however, are shorter, as well as the hind feet. The 
tail is rather longer, and in most cases is uniformly dusky all round, above and below, except 
the terminal third or fourth, while in 7. bulbivorus the tail is grayish white with a dusky line 
running to a point on the upper half from the base. 7". bulbivorus exhibits no wash of very 
dark reddish brown on the back, but is finely mottled with dusky, almost the same on the sides 
and flanks as on the back; instead of having the latter decidedly lighter, clearer, and more 
uniform than the back. The groove on the inner edge of the upper incisor is rather obsolete 
in both, most distinct in 7. bulbivorus. Ido not find any appreciable difference in the skulls, 
except what may naturally arise from the comparison of unequal ages. 
In this species I am inclined to recognize the long lost Geomys wmbrinus of Richardson, 
received by Leadbeater from the ‘‘town of Cadadaiguos, in the southwestern part of Louisiana.’’ 
I have not been able to find this locality mentioned anywhere in North America, not to mention 
Louisiana ; it may be some obscure locality in Texas, Arkansas, or New Mexico, known at the 
date of its reception by Leadbeater, (prior to 1829,) but since forgotten. There are some differ- 
ences from the description to be noticed in most of the specimens. Thus I do not find that the 
fur has the ‘lustre and appearance of that of the muskrat ;’’ nor are the sides of the mouth 
dark brown, the chin and throat white, as described in Geomys umbrinus. On the contrary, 
the chin is sooty black or brown, the throat and under parts usually chestnut. Still, Richard- 
son’s specimen may have presented these variations from the type, and I do not feel willing to 
run the risk of encumbering science with another synonym by proposing a new name without 
further opportunities of investigation. 
G. umbrinus is described as having smooth upper incisors, but I know of no species entirely 
devoid of a furrow, though this may be very obsolete, as is the case with the specimens before me. 
51 L 
