OCR Text |
Show 254 EXPLORATION OF THE OARONS OF THE COLORADO. The longer claws arc much compressed, moderately curved, acute, falcate, or sharp-edged underneath, except at the enrl, where the sides separate with a slight excavation. rrhe back of the hand is moderately pilous, with short, soft hairs; the toes being fringed with rather longer and more bristly ones. The perfectly smooth and naked palm ends behind in an immense protuberance (as elsewhere in the family), which consists, in effect, of an exterior and an interior callosity, united by a slightly-constricted isthmus. This wrist-bulb is overhung by a special tuft. of short, bristly hairs. The sole is naked like the palm, but much narrower and longer (the equality in total length of hand and foot being brought about by the length of the fore claws); it contracts regularly from before behind, ending in a prominent but narrow calcaneum. The upper surfhce of the foot is hairy like the back of the hand. The 3d di~t is longest; the 2d anrl. Lith are subequal to each other, and the tips of theu claws reach about to the base of the middle claw. The lsi and 5th are again about equal to each other, but abruptly much shorter than the others. t~e. tips of their claws hardly or not attaining the base of the 2d and 4t~ d1g1ts. The hind claws are of the same character as those of the hand, but very much shorter. . The tail, as in other species of the family, is surrounrled at base by a comcal en.larg~ment-a prolongation of the body, haired like the rest of the f. ram.e , w.h JCh, m the rutting-season, becomes highly tum1·d unu.1 crneat h, ren d er-m. g It stJll more difficult to say where the tail actua' lly beg1'ns . Me asured f'r om Its true base. a well as this can be ascertained without dissection (from the true ba .e as far as external form is concerned) ' th e t a1' l.I s more t ha n one-th.i rd but decidedly less than one-half' of the lcngtll of h ead an d b od y together-' say about two-fifths. In an average specimen, 7 inches long the tail rna be about 2. 75. Measured from where the lon!Y hair of th b d' ~ . o ' e o y ceases or from Its ~pparent b~se, the tail is about one-third of the length of head a~cl boil Tins member IS somewhat quadrangular the Aatt . . b . . . y. . ' cmng mng espeCially notiCe-able underneath; It gradually tapers to an obtuse ti J ·tnd . 'I . being clothed with short, soft hairs like those cove, I: ' this hpl odus throughout, I h rmg e an s and feet n t e male as well as in the femal t h . . . . in front of th I 1 e, ' e gemtal aperture 18 1mmcrliatcly I . c anus. n t1e rutting- e.,t son, tl 1e en 1a rgernent of the ·trts is c neAy po t-unal; there being a great swelling b h · d tl . P• . tl fi c m le anus winch C'liTtcs 1e anus nway rom the apparent base of th e t at' I · Tll e os pem:s 1. s a sle•n der, J COUES ON GEOMYS AND THOMOMYS-T. TALPOIDES. 255 sharp spicule, clubbed at base, tapering and slightly curved, nearly t~lreequarters of an inch long. In a female, I have distinctly made out twelve mammre, of which two pairs are inside the thigh, two pairs on the chest, anrl. two pairs axillary. Few, however, if any, of the foregoing points are diagnostic of the species; nor will the ensemble serve to distinguish it infallibly from its congeners, , excepting T. clusius. As to form, the single character I notice is the greater average development of the fore claws, bringing the length of the hands up to about t.hat of the feet. Some points of color about to be noticed are the mo~t reliable distinctions. The animal is as nearly as possible like the houserat (Mus decumanus). The whole upper parts are of a uniform grayish-brown, generally quite pure, though occasionally warming into a more reddish-brown. But, in the most reddish specimens, the tint is uniform, without the peculiar mottling or lining of a dark-brown with a red<lish-brown which constitutes the richer color of the Pacific-coast bulbivorus. The only departure from the uniformity of the upper parts is a small blackish patch, usually very evident, in which the ears are set. On the sides of the body, the color gives way grad:.1ally to the lighter tint of the under parts: here we find the plumbeous of the roots of the hairs as a background to a hoary-grayish, resulting from the tips of the hairs. This hoary is usually quite pure, but it sometimes takes on an appreciably muddy-brown tinge, still never equaling, as far as known, the richer fulvous-brown which tones the under parts in the coast form. The tail and feet are white in every specimen I have seen; and, besides this, there are usually patche~ about the mouth, checks, throat, and breast, where the fur is pure white to the roots. But these white markings are wholly inrleterminate in extent, as well as inconstant in appearing at all; in many CilSes, the parts are concolor with the rest of the under surface. Perhaps the strongest color-mark of the species is the absence from any part of the head of sooty-blackish or even dusky areas, there being no noticeable contra •ts of color between the mouth-parts anci pouches; whereas, in T. bulbivm ·us, and, still more so, ·in umbrinus, theRe parts are dusky, or even coal-black, co11trasting sharply with the pure-white linings of the pouches. The whiskers are mostly colorless; the claws are colorless, though usually stained with extravasated bloorl. Northern Dakotan and Minnesotan specimens may be taken to represent |