270 Mr. O. Thomas on some of the 
to be the same smaller form, although a third skin received 
shortly afterwards, and also referred to S$. quachil, now appears 
to be a young individual of the larger. 
Of this larger form the Museum possesses some excellent 
skins from Guatemala, collected by Mr. Salvin in 1865 and 
1873, being those mentioned by Mr. Alston *, and I propose 
to take the best of them as the type. 
Geomys grandis, sp. n 
Size very large, exceeding that of any other known species. 
Fur coarse, as in G. hispidus. Colour smoky chocolate- 
brown throughout, except on the muzzle, cheeks, and chin, 
where the hairs are white or pale whitish brown, Inter 
mixed with the brown dorsal hairs there are, however, a 
certain number of pure white ones, and these seem to be most 
numerous in summer specimens. No darker patches round 
ears. Hands and feet very thinly haired, the few scattered 
bristles whitish. T'ail absolutely naked. 
Skull large and heavily built (see measurements).  As- 
cending processes of premaxillaries surpassing the nasals by 
about a quarter of an inch; the space between them behind 
the nasals less than the breadth of one of them. Interorbital 
space broad, as broad as the muzzle, its edges anteriorly 
rounded and inflated in a manner quite unique f. Zygomata 
not very widely expanded in proportion to the size of the 
skull. 
Incisors pale yellow or whitish, in marked contrast to the 
deep orange found in the allied species. Their single groove 
deep and very widely open, so that its greatest width on the 
cutting-edge amounts to 2 millim.; in position the bottom of 
the groove is internal, the breadth of the inner portion of the 
tooth being about 43 to 45 per cent. of the whole f; owing, 
y) 
however, to the great breadth of the groove itself, it conside- 
rably overlaps the median line, but the above percentage is 
* Biol. Centr.-Amer., Mamm. p. 160. 
+ Most unfortunately the ‘blow of a machete or bush-knife,” with 
which the Indians killed the specimens brought by Mr. Salvin, has exactly 
destroyed the interorbital region in all the specimens except the type; I 
am therefore unable to vouch for the constancy with which the peculiar 
supraorbital inflation is present. 
{ The position of the incisor grooves both in this and other genera 
may be accurately defined by measuring the distance from the hoon of 
the groove to the outer edges of the tooth, and then, the whole breadth 
of the tooth being taken as 100, the proportional breadths of the inner 
and outer portions may be readily calculated. The inner portion per- 
centage of G. mexicanus rises to 47-50, while in G. hispidus it sinks to 
about : 33. 
