. Central Asiatic Expeditions of the American Museum of Natural History, under the leadership of Roy Chapman Andrews : preliminary contributions in geology, palaeontology, and zoology. Central Asiatic Expeditions (1921-1930); Scientific expeditions; Natural history; Scientific expeditions; Natural history. AMERICAN MUSEUM NOV I TATE S [No. 104 Horizon and Locality.—Oligocene, Hsanda Gol formation. Generic Diagnosis.—-Dentition rrrJ- Incisors small, crowded, ? reduced; canines of normal carnivore type, p|- molariform; p^ and P2-3 simple, two-rooted, com- pressed, with sharp cusp and small poste
. Central Asiatic Expeditions of the American Museum of Natural History, under the leadership of Roy Chapman Andrews : preliminary contributions in geology, palaeontology, and zoology. Central Asiatic Expeditions (1921-1930); Scientific expeditions; Natural history; Scientific expeditions; Natural history. AMERICAN MUSEUM NOV I TATE S [No. 104 Horizon and Locality.—Oligocene, Hsanda Gol formation. Generic Diagnosis.—-Dentition rrrJ- Incisors small, crowded, ? reduced; canines of normal carnivore type, p|- molariform; p^ and P2-3 simple, two-rooted, com- pressed, with sharp cusp and small posterior heel, p' with two external cusps. Molars of leptictid type, the trigonid of lower molars composed of two high round, twinned cusps and a small low paraconid, the heel rising sharply at posterior margin to a trans- verse crest, incoilipletely separated into hypoconid and entoconid. M2 slightly larger than mi, heel narrower than trigonid; mi with heel and trigonid of equal width; p4 quite molariform (but the crown less worn and the tooth less fully emerged A7. /9/2^ Fig. 1 . Fig. 1. Didymoconus colgatei, skull and jaws, type specimen, side and top views. The original is somewhat broken and crushed and the distortion has been corrected in the drawing. Oligocene, Hsanda Gol formation, Mongolia. Natural size. Fig. 2. Didymoconus colgatei, upper dentition, c^-m^. Principally from the type skull, supplemented by comparison of several referred specimens. Twice natural size. from the jaw than the one behind it, and therefore assigned to the premolar series), the heel wider than trigonid, and paraconid a little stronger than on the true molars. Posterior mental foramen under ps. Jaw short and deep with strongly sutured symphysis. Upper molars transversely extended, m' consisting of a pair of separate subequal outer cusps, an inner conical protocone opposite the paracone and a strongly developed posterior cingular crest extending somewhat further inward than the protocone.
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