238 EXPLORATION OF THE CANONS OF THE COLORADO. 
feet and tail are mostly whitish (as is always liable to be the case in Geomys). 
There is some whitishness about the lower jaw, and a small white abdominal 
and anal patch; these last being of the irregular indeterminate character often 
seen in and out of this genus. This specimen corresponds exactly with 
Brants's diagnosis of his var. ft. of mexicanus " castaneus, infra canescens, 
maculis auricularibus duabus nigro-fuscis." The same author's var. y. suggests 
hispidus; but it is as well not to strain a point here; for injudicious scrutiny 
of "some of the printed matter extant upon the subject of mexicanus might 
raise synonymatic difficulty with hispidus, 
Owing to insufficiency of material, I am not prepared to pursue the sub 
ject of the characters of mexicanus into the details of variation in size and 
color; but I have no doubt that it corresponds with G. bursarius in these 
respects. 
The specimen shows three pairs of mammae two of which are inguinal 
and close together along the inside of the thigh, the third being pectoral, at 
a considerable distance ; I can find none between. 
This animal is supposed to be the Tucan of Hernandez, with much prob 
ability; and, if so, it was the first of the genus to appear in print. It does not 
appear, however, to have received a scientific designation, or to have prop 
erly entered upon record until many years after li Mus bursarius" had become 
known, when, in 1827, it was called Ascomys mexicanus by Lichtenstein. I 
have met with no specific synonyms, though it has been referred to various 
genera. As the Tuza or Tuca of the Mexicans, it is treated at some length 
in the inedited MSS. of Dr. Berlandier, who, after a good description, says 
that it was supposed by Mocinno and Sesse* (ined.) to be the Mus citillus of 
Linnaeus, and that it is the Taupe mexicaine of which Clavigero speaks. "It 
is destructive in the fields by riddling the ground .... it brings up earth in 
its pouches, and empties them with its fore feet;" and he adds that it inhabits 
the cold and temperate regions of New Spain, and that he never saw the 
Tuza in places where there were squirrels. It is not to be inferred that its 
habits are in any wise different from those of G. bursarius. 
