Exploration of the Colorado River of the West and Its Tributaries Explored in 1869, 1870, 1871, and 1872, Under the Direction of the Secretary of the Smithsonian Institution

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I I k I I 236 EXPLORATION OF TlllU OANONS OF TifB COIJOltADO. GEOMYS MEXICANUS, (Licht.) Lee. Asoomys m.exicamu, LIOUT., Abbaud. K. Acad. Wiss. Borl. 1827, 113.-BUANTS, Muizen, 1827, 27.-WAON., Snppl. flobreb. iii, 1843, 384; iv, pl. 200 A.- CliAlu.EBW., P. Z. S. ix, 1841, 00.-SCIIINZ, Synop. ii, 1fl45, 133. Saocopltoru.s ntcxicamtB, Fiscn., Synop. 1829, 305.-EYn. & Qruw., Go6riu Mag. vi, 1836, 23, pl. 21, f. u, G; Voy. Favorite, v, 1839, 23, pl. 8, f. u, 0.-Rrcn., Rep. Brit. A880o. vi, 1836, 1uO.-GrtAY1 List Marum. Br. Mus. 1843, 160.-GElln., Cat. Bonos Dr. Mu11. 181l2, 223. Pseudostoma (Ocomys) mcxicana, Aun. & DAcn., Q. N. A. iii, 1854, 309. Uoomys 1nc.rioamts, Lv.c., Proc. Acad. Nnt. Sci. Phila. 1852, 160.-DAIRD, M. N. A. 18671 387. Geomys (Saocopltorwt) mc:cicamut, GlEJl., Situg. 1855, 529. 1'ucan of IIEHNANDICZ.-7'ura or 1'uza, MEXICAN.-Titgan apnd Gtcnn., Z. o. Mexicanisclw 1'aschenmanB, OEHl\fAN. DlAGNOSis.-Superior incisors bisected by a single median furrow (as in G. castanops, which is very different in color). Coloration and general appear­ance of G. bw·sarius (which has iwo distinct grooves on ihe upper incisorR). Fur soft, slcel<, as in other species of the genus (excepting G. hispidus, where it is extremely coarse and harsh). Averaging much larger than any United States species (nearly equaling G. hispidus), with proportionally smaller pouches ancl. hands, and weaker claws (these parts being as in G. hispidus). Tail and feet clothed (as usual in the genus), not naked as in G. hispirlus ancl G. tuza. HABITAT.-Mexico. De$C1'iption (No. 3523, Xalapa, De Oca, sldn).-'"fhe general appearance of this animal is so exactly that of an overgrown or ovcrstufferl specimen of orclinary bu·rsarius, that I should be at a loss for terms referring to color t 0 prcci ely characterize it. It is, nevertheless, entirely distinct from this or any other species. It share:;;, with G. custanops, the single median* furrow of the upper inci ors, and some other points of form; but it is much larger, aud altogether of a different color. The excellently well-prepared and not over­stuffed specimen here described is only equaled in a large series oC G. buT­sm ·ius by a single much overstuffed example. The dimension cannot. be given with entire accuracy; but the species probably averages, when full- •o. lli~pidtt8 hna beou described us having at!' rl t]' f upon " single," in antith esis to the donblo furr w '.ng o u~c •an u:row; tho empllusit! here, howev,·r, is t . 'd t 1 o ot 0. btu sartttB, without roforonco to exact pos it ion G uza IS Sill o mvo n. 11 singlo" fnrrow. but t ho · I' . ' r . inner BOCOilll furrow USU" IJy SOCII I a' , propor lrTlp ICI1tJOn it! moroJy obsoleteness of tbo fine .. · n . mcxwautts nH in (.' ca 1 1 f · median; in 0. hiHJ>idns, Hiuglo noll internal ; in G. ,,;a, appm·~ntl; :;:~;:~ ~~:~ ,.:~:~~~:1~s truly Bingle nml .. COUES ON GEOMYS AND 'l'llOMOMYS-0. MEXICANUS. 237 gruwu, about 10 inches from no~e to root of tail. Tail about 3 inches from its apparent base (LeCont.e gives i1s 1eng1.h as 5 inches); sole, somewhat cramped, apparently 1.50 ; hand, much cramped, estimuteJ to be about the sa.me, or rather less. Nose to eye about 1.31'>. Girth of body 8 or 9 inches. The pouches, as well as can be judged from the skin, arc smaller proportion­ally than those of the United States species; in this respect, being like those of G. Aispidus. These two Mexican species further agree iu the relative smallness of the hands and less enormous development of the claws; the fore member being shorter, or, at most, not longer, than the hinder one. '!'he vesture of the feet and tail is much the same in extent as in bursarius, and t hus in t:tr·iking contrast to those parts in either G. tuza or G. hisp1:dus. The orifice of the ext ernal ear presents, in the dried state, a mere rim, around which no flap can be fairly recognized. It seems preferable th us to describe this species in comparative terms to bring out the curious interrelations of the animal-a species with the size aud single incisor-fu rrow of G. hispidus, yet I he furrow different in po~ition, and the pelage altogether different. Agreeing in the points of character of pelage, its color, and amount of hairiness of tail and feet with G. bursa'n;us, yet at once distinguished by its superior size and single median furrow of the uppqr front ieeth; exactly like G. cQ))tarwps in t his last respect, and in most others, yet entirely of a different color; disagreeing wi th all the United States species in its smaller pouches and weaker hands, and in these points agreeing with its very di ti nct Mexican congener. As regards color: LeConte's animal, "which agrees with Lichtenstein's and W agncr's description , " and is call eel ''saturate cinereus, supra nigro-tinctus, naso brunneo," was evidently an example of ihc '' plumbago"-colorcd variation, which may occur in any species of this genu nn well as in Thomomys. 'f lte specimen before me is of the normal coloration ; and this cannot readily be characterized as any thing decidedly different from orcl iuary bursarius, though there is a purity of the che8tnut-brown which contra.sts with the muddy brown (in some cases almost a glaucous shade or "bloom") commonly seen in bur­sarius. All th e fur is clccp plumbcous ba 'ally, pointed with the warm brown on the upper part , and only partially hidden below by muddy gray and hoary cuds of the huir!:!. '!'here i · a Jarkues about the auricu lar region. 'rhc hind