. Bulletin - American Museum of Natural History. Natural history; Science. 2o6 Bulletin American Museum of Natural History. [Vol. VI, Aceratherium platycephalum, sp. nov. i'i \n. ii. /â :. The type of tliis species is a skull and lower jaw (No. 545) from the coarse sandstones or lower section of the ' Protoceras Beds," on the same level with A. tridactylum. Belonging to the same spe< ies is a perfect sel of upper premolars and molars of the right side ( No. 540). The specific distinctions are as follows : I 'entition, ':., ", [ .,,;':. (a) Third ami fourth upper premolars with pro
. Bulletin - American Museum of Natural History. Natural history; Science. 2o6 Bulletin American Museum of Natural History. [Vol. VI, Aceratherium platycephalum, sp. nov. i'i \n. ii. /â :. The type of tliis species is a skull and lower jaw (No. 545) from the coarse sandstones or lower section of the ' Protoceras Beds," on the same level with A. tridactylum. Belonging to the same spe< ies is a perfect sel of upper premolars and molars of the right side ( No. 540). The specific distinctions are as follows : I 'entition, ':., ", [ .,,;':. (a) Third ami fourth upper premolars with prominent postero-internal cusps (tetartocones) which when unworn are quite separate from the delicate posterior crests ; third premolar quadrate ; fourth premolar subquadrate. (6) Internal cingula upon true upper molars wanting- ; first molar exhibit'- an ' antecrochet ' ; third molar exhibits a depression on the posterior face at the junction of the ectoloph and metaloph. (c) Large procumbent lower canines, with a --mall median pair of incisors. (\ two low. divergent tinea <rp,:-<i about one inch apart. Both spe< miens ( Niis. 545, 540) belong to a large animal. The skull is about 25 inches in length, and is wholly different in its proportions from that of the con- temporary A. tridactylum, which is of the high narrow type, and about 20 inches m length. The prominent bosses above the post- orbital processes, the short obtuse nasals, the verj large horizontal lowet in< isiMs. ,o 1 .mines, the Bat- tened upper surface of the 1 1 1 niuin. a re all < his w hieh immediatel) distinguish this type. The proportions of the skull suggesl that this spe< ies ma) have su< 1 eeded the .7. mite Cope. The last upper molar is somewhat similar in form to that of . / umplicidens < m 2 /H3 â I third uppi ol A ., rather in in sinr/- type. One-half natural size. Aceratherium tridactylum Plate II, A. nni'nu ill. This spe< ies was founded upon tin- rem
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