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Show 234 EXPLORATION OF THE CANONS OF THE OOLORADO. tail sparsely pilous. Color pale yellowish-brown above, inclining more or less to dull chestnut about the head; whitish below. Size of G. bursarius, or rather less. Fur soft, as usual in the genus. HABITAT.-rrexas and New Mexico. Description (from Baird's types of G. Cel$tanops and G. clarkii, and other specimens).-This remarlmble species is immediately distinguished from all others known to me by the combination of a single median groove of the incisors, pale light color, and small size. In the first-named particular alone, it agrees with G. mexicanus; in both these species, the single groove is central, bisecting the surface, so that, viewed from the front, there appear to be four incisors. This at once and permanently separates it from G. bursarius, with which it is to be compared in other re pects. In size, the five specimens before me averuge about the same as G. bursa·rius, though none are as large as the largest of the latter I have seen. The length of the full -grown animal may be about 8 inches, rather less than more; and some are not much over 6 inches. The tail, as well as can be judged, is 2 ~ to 3 i nchcs. A notable peculiarity of form, in comparison wi1 h G. bursarius, lies in the relative proportions of the fore and hind feet, which are much as in GG. mexicanus and hisp£dus; the palm, with the length of claws included, being shorter, or, at most no longer, than the sole and claws; the latter measuring about 1! inches, the tormer only about 1! inches. The fore claws are, however, well developed proportionally, no difference in this respect from G. bursa'rius being readily appreciable. The external ears may fairly be called obsolete; in neither of the specimens can I make out anything more than a thickened rim surrounding the orifice of the meatus. The hairiness of the tail and hind feet is pretty much a in an average specimen of G. bu·rsarius or G. mexican us; they arc thinly clothed indeed, but noticeably more so than is ever the case with G. tuza or G. hispidus. The pouches are somewhat less ample, apparently, than in G. burt;arius-a character coordinated in this genus with weaker fore feet and seen also in G. mexicanus and G. hispidus. ' The coloration merits particular attention, not only as it is the next to . the strongest character of the species, but because a casual pha:-<c of it was the basis of the original Pseudostoma cnstanops. It might seem surprising and certainly it would be contrary to analogy, that a single species of this, un1- COUES ON HEOMYS AND TBOMOMYS-G. OASTANOPS. 235 formly-colored family should exhibit u sharply-defined" or "symmetricallysubcircular" areas of color; and such proves not to he the case. The type of Pseudostoma castanops, now before me, in a good state of preservation, notwithstanding the vicissitudes of thirty years of museum existence, though bleached by long exposure to the light, still shows the curious chestnut headpatches, sharply defined against pale tawny-white surroundings, just as describerl at length by Professor Bairrl. But the animal was shedding its coat when killed; hence the appearance. The new fur is brightly colored, contrasting with the old faded and worn pelage.* One of the types of ''clarkii" has the same color of the head, but this is also diffused with somewhat rliminished intensity over the whole upper parts. Other speeimens are entirely similar, with various shading of the main color. This may be described as a dull. pale chestnut, or almost fin.vn-color, more or less shaded with the plumbeaus basal portions of the fur, which usually show more pr less in this genus, be the fur never so smoothly laid. This tawny or fulvous tone of color is highly characteristic in comparison with the cleeper and warmer chocolate or muddy browns which G. bursarius shows. On the under parts, though the plumbeous basal portion of the fur shows consiclerably, the gct~eral tint is whitish-quite white in comparison with the muddy gray of the arne parts of G. bursarius. Tho whiskers are mostly colorless; they are fine and numerous, the longest about equaling the head. The claws are pale horncolor; the naked palms and soles show various discoloration, perhaps according to the quality of the soil worked in. The incisors arc orange, as usual. The few specimens of this species known to naturalists were procured in Texas and New Mexico. rrhe animal would appear to be comparatively rare, as very few individuals, adrlitional to those de cribcd by Professor Bairrl, have ever been collected, though we have plenty of the Thomomys (umbrinus). of the same region. The written history of the species is brief and precise; determination of the identity of cladcii with castanops leaves nothing to be &aid on the score of synonymy. Castanops is to be retained as the prior name, and is unobjectionable, though it has proven not particularly pertinent. • Various spooimons of GconlyB and Thomomy8, changing polt\go, show curious sllf~orp wandering Jines whore the old and now fur fail to moot and fit exaot.ly ; and such lines are often observed when the pelage appears to bo all of an ago. |
