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Show 218 BXPLOHA'l'ION OF TilE UANONS OF THE UOLORADO. mo-t nearly allied, family. The Saccmnyidcc arc extremely lithe, agile, graceful animal·; j rboa-like. with long . alta to rial hind limb~, elongated and often tufted tail, large cars, and full eyes, and are not specially nocturnal or subterranean in habits. The Gl'Ornyidm, on the other hand, nrc halllstcr-lik ', or rather an exaggeration of that kind of structure; they arc nmoug the heaviest fur their inches of any animals of this count.ry, of squat, bunchy shape, with short, thick limbs, a "hart tail, very small or rudimentary ears, small eye, no a pprceiablc neck, and thick, blunt hcacl; and they are as com pletcly subterranean us the mole it elf: They are rarely and only momentarily seen above around; they excavate cnulct:~ galleries in the earth in their search for food, frequently comiug to the . udi1cc to throw out the earth in heaps, but plugging up the e orificct) as soon us they have served their purpose. Both fiunili~s agree in po sc sing enormous cheek-pouches, overlying the whole side of the head, in some species even reaching over the necli. and shoulders. The nature and construction of these sacs was long misunderstood. rrhcy were supposed for many years to be external pendulous bags opening into the mouth, and thu::s to differ only in degree of development from the ordinary "cheek-pouches" of many other rodents-an enlargement of the mucous membrane of the mouth and skin of the cheeks. But, as now well known, they have no connection with the mouth; at least, no more than the ahdo111inal pocket of an opo sum has with the genitalia. Their chief purpose i~ not even related to the food of the species; they are sacs that the animals usc chicny in carrying out dirt from their burrows to deposit it on the surface of' the ground. They arc fully described beyond. Several circumstances have conspired to obscure the history of the Geomyi.dce, and to involve the determination of the species in doubt. In the fir ~t plt~<·e, the animals are largely withdrawn from orclinary observation, and · the acqui ' LI ion of pecimcns is difficult. Their geographical distribution is limited to a port ion of America. V cry few specimens, comparatively, have ever reached Europe, and very few foreign naturalists have written about them from any I hi ng like ufficicnt me·a us of observation · I n rm. e t, ~"11 cy arc among the rare. t . cts of specimens in any museums; and I think it probal>lc that there are before me, as I write, more prepared specimens than have before b en cxnmi nc<l hy all naturalist· put together. This shows the , COUES ON GEOMYS AND TIJOMOMYS. 219 oifliculty of getting material to work upon on thi family, though the animals fairly f.lwarm in certain regions, becoming a serious hinderance to agriculture. rnwrc is another point to be considered here: the :shapelcssnc s of the species, so to speak, with the looseness and di tcnsibilit.y of the skin, renders them peculiarly susceptible of atrocious taxidermy, with the resu lt of scarcely leaving a hiut of their actual appearance and true dimensions. One result of all thi::s is that a mass of pointless, if not crroncou , de;;cription and conflicting accounts form u large part of the written hi~tory of the species. '!'here appear" to have been an unu ually large amount of compilatiou done in t his group; more than half of everything extant upon tho subject is of this character.* The ' ystcrnatic '' acco unts given by Fi cher, Schinz, Wagner, Giebel, and ~orne others that might be named, are simply worthless for any practical pu rpo c. rrhc special papers upon the subject are so few that it was not thought ncccs .. ary to enumerate thcrn. Aside from the descriptions of "new species" which it is nccc::;sary to examine, the authorities which need be consulted arc very few. Waterhouse's and Brandt's articles; especially Richard on's, in the Fauna Borcali-Amcricana; LeConte's monographic sketch of the family; and Baird's later, more elaborate, memoir, with Audubon's and Bachman's figures, represent the gi t of the matter. r:rhe synonymy collated in this paper is believed to represent very nearly all the literature of the su bjcct. It is not within the scope of the pre cnt article to treat fully of the characters of tho family. I confine myself here alma t entirely to the determination of the species and t heir full description, with t.he 11ccessary bibliographical matt er. The number of species I find to have been, much as usual, largely overstated. This is particularly the ca e in tho genus Tltomomys, where the three recognizable races of tho inglc known species have been lle:scribed as a dozen distinct species, and been re ferred to half as many different genera. Most late authors recognize at least six or eight species of the genus. Geomys makes out a better case; out of the seven !o~pecies ad mittecl by Baird, five arc unquestionably valid. It is very curious an<l interesting to note how differently Geomys and Tlwmomys have become differen~ iutcd into .,pccics. The former gen us ha clevcloperl into at least five "Cj. tho 11ynonymy of Tllomomys ta.lpoide11 ct a.ff. in t.uo following p::tgt•s. |