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Show 222 EXPLOUATlON OF 1'llE OARONS OF THE COLORADO. of the fur plumbeous throughout; or blackish-gray; feet and tnil, for the most part, white or colorless. Average dimensions of adult, 7 to 8 inches; tail, 2 or 3 iuches; fore foot, about 1~ inches; hind foot, about 11 inches; longest fore claw, about 0.75 inch. HABITAT.-Vallcy of the Mississippi and its tributaries in a broad sense, and somewhat beyond to the northward. "Canada." "Oregon" (111). DgscRIPTION.-I shall draw up my account of this species from the large amount of material, both dry and alcoholic, before me. The specimens are from the whole immediate valley of the Mississippi, from the State of that name to Minnesota; also, from Tcxns ; from the Platte, Washi ta, and Niobmrn Hivers, &c.; but uot from west of the Rocky Mountain~, where the gcu us has yet to be satisfactorily determined to occur. Descriptions of fon~ and proportions are taken from alcoholic specimens in the Ac:sh ; of color, from dric<l specimens. The pre ent being taken as the standard of comparison for other species, succeeding descriptions of the rest may consequently be abridged to present in stronger light their own peculiar characters. The present account, besides being descriptive of the particular specie~, is rendered supplementary to the characters of the genus. The "pocket-gopher'' is about the size of a house-rat (Mus decurnanus) but less in linear dimensions and much more "~ toutly b u 1' I t , w 1't l1 a he a v y,' lumpy hody, on which the skin slips loo ely; no appreciable neck; a rapidly narrowed blunt head; Arnall eyes ; no obvious external ears ; short limbs; strong fin·c feet, somewhat like those of n mole w1, 'th e, normous c1 a ws · an d a ~10rt, . t hick, stumpy tail, issuing from a conical prolongation of th~ rump. 1 he .stele of th~ bod~, before the shoulder, is occupied by an enormous sac, ope. ning b. y n Wlflc . lit along the side of the J'•a ws , but not d1' rec tl y commum· - cating with the mouth. These sacs, fully di temied represent the t t crot'"S 'vVI·S C d't mensw· n of the anu. nal. 1,o sum th, ' l' t' - ·h , grea · es . c genera t tes, t c gopher 1s a mole-like rat, plus these great bagl'l. 'rhe general habits bear out the simile . of all rodents, tl~c gopher is probably the must completely fos ·orial ancl sub~ terrancan ·' and 1ts undercor roun d operati·O ns are conducted with the 'd f these sacs. m o The head i ~ short wirle d d bl . ' ' cep, an un t ; not separated from the bod by any apprecmblc constriction of the neck 'rll f'· t l . . y · 0 1 on a regwn IS broacl and OOUES ON OEOMYS ANJ> TUOMOM YS- G. BURSAlUUS. 223 nat; the ides rapidly converge · the under side and mouth part arc anomalous in thei r peculiar configuration. Tho muillc i enti rely hairy, excepting u. Rmall, definitely naked nose-pn<l, somewhat ~- hnpcd, with long arms and a short leg; the nostrils opcni ng obliquely between t.hc c. There is a considerable hairy interval bctwc~n this pad and the incisor8, and a fringe of long hai rs hangs down over these teeth. '"rhc upper incisors appear to be situated remote from the mouth ; for beneath them is n long strip of finely furry skin, longitudinally vau lted, with sides sloping upward to a median line, like the roof of a house wit h its rirlge. This great space, near an inch long, bounded on either side by the swollen furry ridges which constitute the cxtcrnallips, leads to the contracted orifice of the mouth proper, or that part of the buccal cavity lined by mucous membrane, to which the p·arts j ust described are merely the vestibule. .The mucous membrane only comes to · the border of the t hick external lips in a small patch on each side. '!'he lip laps loosely around the base of the under inoisors, and the opposite sides meet behind the teeth. In fact, the curious conformation is uch that the mouth actually shuts idcways by approach and meeting of the thick lips from either side; further closure of t he jaws resulting in merely a fo lding back of the thus apposed lips. When t he mouth is closed, the incisor teeth are entirely shut out of the buccal cavity, and surrounded behind, as well as elsewhere, by furry integument ; in a la rge specimen, with the tips of the incisors in apposition, t.hc end of one's finger may be paRsed behind them, yet not into the · mout.h at all. On wrenching open the jaws, the neshy tongue is seen largely ftlling the remarkably contracted true orifice of the mouth; but so constricted i8 the opening that t he molar dentition can scarcely he brought into this VICW. rf'hi particular COndition of the parts is probably not met with OUtside the present family. 'r hc pouches of this species- at fi rst supposed to be pendulous bags hanging from the mouth, t hen with some correction fo und to he not pendulous, yet believed to open into the mouth from within- arc wholly external, ancl have no more connection with the buccal cavit.y than the belly-pouch of' a kangaroo or opossum has to do with the genital organs. These sacs nrc simply a pur c- hapcd duplicaturc of the loose skin of the siue of the head attd Itcck. The f'rcc margm of tlw pouch arises from the side of the upper |
