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Show COUES ON GEOMYS AND THOMOMYS - G. BURSARIUS. 223 flat; the sides rapidly converge- the under side and mouth parts are anomalous in their peculiar configuration. The muffle is entirely hairy, excepting a small, definitely naked nose-pad, somewhat T-shaped, with long arms and a short leg; the nostrils opening obliquely between these. There is a considerable hairy interval between this pad and the incisors, and a fringe of long hairs hangs down over these teeth. The upper incisors appear to be situated remote from the mouth; for beneath them is a long strip of finely furry skin, longitudinally vaulted, with sides sloping upward to a median line, like the roof of a house with its ridge. This great space, near an inch long, bounded on either side by the swollen furry ridges which constitute the external lips, leads to the contracted orifice of the mouth proper, or that part of the buccal cavity lined by mucous membrane, to which the parts just described are merely the vestibule. .The mucous membrane only comes to the border of the thick external lips in a small patch on each side. The lip laps loosely around the base of the under incisors, and the opposite sides meet behind the teeth. In fact, the curious conformation is such that the mouth actually shuts sideways by approach and meeting of the thick lips from either side; further closure of the jaws resulting in merely a folding back of the thus apposed lips. When the 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 large specimen, with the tips of the incisors in apposition, the end of one's finger may be passed behind them, yet not into the mouth at all. On wrenching open the jaws, the fleshy tongue is seen largely filling the remarkably contracted true orifice of the mouth; but so constricted is the opening that the molar dentition can scarcely be brought into this view. This particular condition of the parts is probably not met with outside the present family. The pouches of this species-at first supposed to be pendulous bags hanging from the mouth, then with some correction found to he not pendulous, yet believed to open into the mouth from within-are wholly external, and have no more connection with the buccal cavity than the belly-pouch of a kangaroo or opossum has to do with the genital organs. These sacs are simply a purse-shaped duplicature of the loose skin of the side of the head arid neck. The free margin of the pouch arises from the side of the upper |
