r 



'« 



,; 



108 



MONOGUArUS or NOUTII AMEUICAN ItODKNTIA. 



spiMMc^H wn have Imd the ploasuru of adding a now and interesting variety, if not 



species, from a iiitlierlo nnsuspect(!(l locality. Tiic following uro tlicconiimr- 



ativ(! diagnoses of the two forms: — 



Beneath, snow-white ; above, mouse-brown, with darker 

 dorsal area Tail twice the hind foot or less; much 

 less than half llu; head and body. Fore foot more 

 than half the hind foot. Ear about 0.50 high leucooasteb. 



Beneath, tawny-white;* al)ovo, brownish-fulvous, with no 

 darker dorsal area. Tail about t ^o and n lialf times 

 the hind foot; almost half us long as the iiead and body. 

 Fore foot half the hind foot. Ear nl)out 0.75 high (van?) torriuub 



n '^■- it 



IIESPEROMYS (ONYCHOMYS) LEUCOGASTEli (Maxim.). 



Hl88oarl Molc-Monse. 



Ilillimlirun IciicogaKlcr, Maximilian, IMm in iliw Iiinero N.-Ainrr. ii, 1811, iKt (Fort Clark). 



//(■»j«Torai/« (Onjivhomiiii) tciicogaflir, Baihd, M. N. A. IH57, 4S0 (Nebrusko).— CoUKS, Proo. Aciul. Nut. Sci. 



rii'ilii. 1874, lti2. 

 HiiipiromijK Ituwganlcr, Maximilian, Arch. Niitiir),'. nviii, lMi2, pi. 4, f. 8 ; Verz. N.-A. SUur, m>'i, l«l, Hg. 

 Una mmoiinVimi*, Aui>. & lUcil., Q. N. A. ii, 1851, 327, |il. 100 (Fort Uniun). 



IIahitat. — Upper Missouri region. Red River of the North (Coues). 



Our notice of the subgenus Onychomijs has necessarily involved the 

 details of its type-species so largely that but little r(!mains to be added. The 

 absolute dimensions and relative i)roportions of several specimens, most of 

 them additional to any heretofore published, are fully elucidated in the 

 following table. 



In color, the animal closely resemhhs IIi'sperom>/ii /eiicopug — so closely 

 that it is (litticult to describe any ditlerences. When young, it is of the same 

 pluml)eous-gray above and ashy-white beneath ; and, with advancing age, 

 these colors change to snowy-white below and fulvous-brown al)ove, wilii n 

 dusky dorsal area. Tlie feet are white ; the tail is bicolor ; the whiskers arc 

 black, with a few white ones intermi.xed. The chief distinguishing feature 

 in coloration, as compared with Hesperomy.i kucopus, is the mostly wiiite 

 muzzle. In leucopus, the white usually slopes down to the lips, leaving the 

 nose of the color of the forehead ; while, in leucogaxter, the white keeps on, 

 niid embraces the snout. This curious difTerence holds good in all the speei- 



•As intdui.;ted beyond, no are not pcilV'tily gum tliat the .vcllowish tiut isnot due tudiiicoloia- 

 tiou in olooUol. 



Hv.l 



! ; 4f» 



'=1 



