176 BULLETIN NO. VII. 



GENUS VESPERIMUS, COUES. 



A word of explanation is necessary in thus employing the 

 name usually considered subgeneric under Hesperomys as of full 

 generic value. This change was the result of an attempt to 

 diagnose the genus Hesperomys as it now stands in our litera- 

 ture, with the groups Vesperimus, Onychomys, Oryzomys, Calomys, 

 Habrothrix and Oxymicterus as subgenera. It was found impos- 

 sible to distinguish these genera collectively from the associated 

 genera by any characters of a higher sort than those separating 

 them among themselves. In this dilemma the simplest remedy 

 seemed to be to disregard altogether the generic name 

 Hesperomys, which was, as pointed out by Baird,orginally applied 

 to the whole group of Sigmodont Muridce. Moreover, Hesperomys 

 would need to give place to the prior name, Sigmodon, if its sig- 

 nification were simply restricted to the whole group to which 

 it could naturally be applied. Sigmodon, however, is duly rec- 

 ognized as a valid generic term, and for our part we do not see 

 that any harm can result from the change proposed. 



The genus Vesperimus was amply characterized by its founder 

 and, as by him diagnosed, includes animals of medium or small 

 size, lithe form and quick movement. The long hind legs and 

 rather short anterior extremities adapt them for rapid running 

 and springing, while the short fore claws indicate that they are 

 not fossorial. The fore feet are rather less than half as long 

 as the six tubercled soles. The palms are naked, while the 

 soles, in most of the species, are furry posteriorly. The tail is 

 usually long as compared to other native mice, ranging from 

 considerably longer than the remainder of the body to the 

 length of the trunk alone. 



The head presents an animated appearance. The bright 

 prominent eyes, large sparsely pilous ears and acute muzzle 

 conspiring to give vivacity to the face. The ears are unusually 

 large and thin. The colors are bright, and the contrast between 

 the upper and lower surfaces of both body and tail is marked. 



The most unreflecting person would be forced to admire the 

 sprightly deer mice, and they universally attract attention, 

 while their inroads upon the graneries are rarely so great as 

 to merit the execration poured upon their domestic cousins. 



The cranial and other anatomical characters maybe gathered 

 from the specific description beyond ; a few points only need 

 be noticed. Characteristic features are the slender rostral 

 part occasioned by development of the nasals and premaxilla- 

 ries, the broad, low, cranial portion, and deflected zygomas. 



