234 EXPLORATION OF THE CANONS OF THE COLORADO. 
tail sparsely pilous. Color pale yellowish-brown above, inclining more or 
less to dull chestnut about the head ; whitish below. Size of G. bursarius, or 
rather less. Fur soft, as usual in the genus. 
HABITAT. Texas and New Mexico. 
Description (from Baird's types of G. castanops and G. clarkii, and other 
specimens). This remarkable species is immediately distinguished from all 
others known to me by the combination of a single median groove of the 
incisors, pale light color, and small size. In the first-named particular alone, 
it agrees with G. mexicanus ; in both these species, the single groove is cen 
tral, bisecting the surface, so that, viewed from the front, there appear to be 
four incisors. This at once and permanently separates it from G. bursarius, 
with which it is to be compared in other respects. In size, the five speci 
mens before me average about the same as G. bursarius, though none are as 
large as the largest of the latter I have seen. The length of the full-grown 
animal may be about 8 inches, rather less than more ; and some are not much 
over 6 inches. The tail, as well as can be judged, is 2J to 3 inches. A nota 
ble peculiarity of form, in comparison with G. bursarius, lies in the relative 
proportions of the fore and hind feet, which are much as in GG. mexicanus and 
hispidus ; the palm, with the length of claws included, being shorter, or, at 
most no longer, than the sole and claws ; the latter measuring about 1 J inches, 
the former only about 1 J inches. The fore claws are, however, well developed 
proportionally, no difference in this respect from G. bursarius being readily 
appreciable. The external ears may fairly be called obsolete ; in neither of the 
specimens can I make out anything more than a thickened rim surrounding 
the orifice of the meatus. The hairiness of the tail and hind feet is pretty 
much as in an average specimen* of G. bursarius or G. mexicanus; they are thinly 
clothed indeed, but noticeably more so than is ever the case with G. tuza 
or G. hispidus. The pouches are somewhat less ample, apparently, than in 
G. bursarius a character coordinated in this genus with weaker fore feet, 
and seen also in G. mexicanus and G. hispidus. 
The coloration merits particular attention, not only as it is the next to 
the strongest character of the species, but because a casual phase of it was 
the basis of the original Pseudostoma castanops. It might seem surprising, and 
certainly it would be contrary to analogy, that a single species of this uni- 
