. 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. 1925] FAUNA OF GASHATO FORMATION, MONGOLIA 9 Paratypes.—No. 20430, symphyseal parts of three lower jaws. A number of skeleton fragments are also referred here. Characters.—Molars lophodont, rather low-crowned. Upper molars with six cusps, three in the anterior crest, three in the posterior,
. 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. 1925] FAUNA OF GASHATO FORMATION, MONGOLIA 9 Paratypes.—No. 20430, symphyseal parts of three lower jaws. A number of skeleton fragments are also referred here. Characters.—Molars lophodont, rather low-crowned. Upper molars with six cusps, three in the anterior crest, three in the posterior, and a prominent mesostyle continuous with the posterior crest. Basal cingulum continuous around the tooth. (This structure is best shown in m^, which is slightly larger than the others.) Lower molars composed of two slightly oblique cross-crests and a small, low heel; the crests consisting of an external and an internal cusp, the former having an oblique wing running inward and forward, much as in Eohippus. Premolars narrower and smaller than molars, the size and relative width of the teeth increasing uniformly from ps to m3. Anterior premolars not known, except for the roots in the paratypes, which indi- cate a continuous unreduced series without diastema. Canines considerably enlarged, incisors not preserved, presumably small and verj' likely reduced in number or wholly absent. AM Z04I2. Fig. 11. Phenacolophus fallax, new genus and species. Occiput, posterior view. No. 20412. Natural size. Among the skeleton fragments doubtfully referred to Phenacolophus is a calcaneum of very singular type, comparable to some degree with Periptychinse and Ectoconus, more closely with Isotemnidse of the South American Eocene. It is short and massive, with broad fibular facet at a very low angle with the astragalar facet, which is neaiiy flat and in the same plane with the sustentacular facet; and the cuboid facet is very strongly oblique, facing more internad than distad, and is moderatel
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