442 ["December, 



Description of two new species of Ilesperomys. 



By John Le Conte. 



Dr. Bachmao, ia Audubon's Quadrupeds of North America, states that the 

 Hesperoinys leucopus inhabits the southern regions of our country. Although 

 I have resided in the lower part of Georgia for a great portion of my life, I never 

 saw it there. There are however two species which he seems to consider the 

 same, and which he has confounded with the northern animal. An accurate 

 and detailed description of these will show very distinctly how much they differ. 

 These two species are the gossypinus and the cognatus. The first was described 

 by me in the Proceedings of the Academy, vol. vi. p. 411, and is very easily 

 distinguished from the other by its larger size. The second, which I was led by 

 the assertion in the Quadrupeds of North America to consider as the Hesper- 

 omys leucopus, a more careful examination and comparison have shown to be 

 entirely distinct. It appears in some degree allied to the H. gossypinus, but its 

 manners are very different. 



H. COGNATUS. 



Hair dark plumbeous, above tipt with dusky and rufous-brown, with the 

 latter more particularly on the sides, beneath with white, but in such a manner 

 that the dark color of the lower portion of the hair shines through tbe 

 white. Head large rather blunt, upper half of the cheeks inclining to rufous, 

 ears large, open, naked except the lower part of the outer edge, feet flesh-color, 

 tail slightly hairy, beneath whitish. 



Length 3.4 in. Tail 2.2 in. Head 1.2. Fore leg 1.1. Hind leg 1.6. 



This animal is easily distinguished from the H. leucopus by the under parts 

 never being of the pure and snowy whiteness that gives so much beauty to the 

 northern animal; they are however very nearly related. The relative difference 

 of the fore and hind legs is not so great as to cause it to leap and not to run 

 when endeavoring to escape pursuit. In size its dissimilarity to the H. gossy- 

 pinus is most remarkable. This last also has tbe under side of the tail pale 

 brown. The other likewise wants tbe narrow whitish border to the ears. 



Inhabits Georgia and South Carolina; in the winter it frequents houses like 

 its analogue in the north. 



I have the pleasure to add to our daily increasing Fauna another species of this 

 genus which I have received from Michigan. It likewise appears somewhat 

 allied to H. leucopus but has very distinctive characters in its colors. 



H. GRACILIS. 



Hair dark slate-color above, a little tipped with brown, cheeks, line above 

 the mouth, chin, throat and body beneath white, allowing the dark color of 

 ihe lower part of the hair to shine through in such a manner as to cause 

 these parts to appear grey. Outer side of fore legs brownish, thighs slate- 

 < olored both above and beneath, feet pale grey, nearly white. Head narrow, nose 

 somewhat pointed, ears large, open, narrowly edged with whitish. Tail longer 

 than the head and body. 



Length 3.8 in. Tail 4 in. Head 1.2. Ears .6. Fore leg .1. Hind leg 1.5. 



Inhabits Michigan ; Prof. Baird. 



We have in this genus three species which resemble each other. I have added 

 below, short diagnostic marks by which they may be easily distinguished. 



H. leucopus, supra laete badius, interdum prope aurantiacus, subtus niveus, 

 coloribus a se abrupte disjunctis, pedibus posticis anticis plus duplo longioribus. 



H. cognatus, supra nigro-fuscescente, et fusco variegatus, subtus albidus 

 tanquam cinereo-mixtus, pedibus nontam imparibus. 



H. gossypinus, supra fuscescente-badius, lateribus dilutioribus, subtus 

 cinerascente-albidus. Corporis magnitudine valde a duobus precedentibus differt. 



