208 BULLETIN NO. VII. 



of fine grass. It is not so securely built as the nests of some of 

 the other species of this family. Cooper's mouse lives in winter 

 chiefly upon the stems of blue grass and the more tender por- 

 tions of white clover. In November, 1883, a large quantity of 

 the tuberous roots of the "Wild Artichoke" (Helianthus doro- 

 nicoides) were found in the storehouses of a colony of these 

 mice. 



GENUS ONYCHOMYS, BAIRD. 

 MOLE MICE. 



This genus is of particular interest in as much as it contains 

 three varieties of mice which, from their inaccessible station 

 and secluded habits have seldom gained admittance to natural 

 history museums or received the attention of naturalists. This 

 interest is enhanced by the fact that the genus is evidently 

 very closely allied to Vesperimus but has developed in a direc- 

 tion entirely different from that group ; and its species, exter- 

 nally and in habits, vary greatly from the deer mice. Fossorial 

 prairie or desert animals living largely on insects might be 

 expected to differ greatly from such saltatorial and gramnivor- 

 ous animals as Vesperimus contains. 



The mole mice are distinguished from their relatives by the 

 compact arvicoline form, short tail and hind legs, well de- 

 veloped anterior extremities with fossorial claws, and the soft 

 mole-like character of the pelage. The hasty observer would 

 refer the animal to Arvicolince rather than to the sigmodont 

 Murince ; indeed prince Maximilian, who was the first to meet 

 the genus, referred the 0. leucogaster to Hypudceus. As we 

 have specimens of none of the genus except 0. leucogaster var. 

 pallidus the reader is referred to the discussion of that variety 

 for a description of the anatomical peculiarities. It seems 

 that, in view of the many points of divergence in structure and 

 habits, there should be no hesitation in separating the mole 

 mice generically from Hesperomys. 



Onychomys leucogaster MAXIMILIAN. 



MISSOURI MOLE-MOUSE. 



Hypudceus leucogaster MAXIMILIAN, Reise in das Innere N. America, 1841. 

 Mus missouriensis AUDUBON AND BACHMAN, Quad. N. A., 1851. 

 Hesperomys (Onychomys) leucogaster BAIRD, Mam. N. A., 1857. 



COUES, Proc. Acad. Nat. Sci.Phila., 1874; Monogr. N. A. 



Rodentia, 1877. 

 Hesperomys leucogaster MAXIMILIAN, Arch. f. Naturg. xviii, 1862. 



