1902.] 



Osborn, American Eocene Primates. 



185 



are somewhat more primitive than those found in the Bridger 

 in the more triangular shape and less prominent development 

 of the hypocone. The hypocone is stronger than in the Was- 

 atch specimens and both third and fourth premolars exhibit 

 deuterocones. It is therefore probable that there are valid 

 specific differences between these animals and the overlying 

 Bridger species. 



(Sp. 55) Hyopsodus wortmani, sp. nov. 



Type No. 4716, Am. Mus. (figured by Cope as H. vicarius), Fig 11. 

 is valuable because it shows a 

 complete maxilla and premaxilla, 

 the latter with three incisors of 

 which the median pair is possibly 

 slightly enlarged; the crown of 

 the second incisor preserved is 

 pointed. Third superior premolar 

 narrow with a deuterocone. Su- 

 perior ms = 10 mm. Inferior pms — 

 ms = 21 mm. 



The best specimens in the 

 American Museum collection are 

 Nos. 4716, 4712. Inferior true molars measure 11 to 13 mm. 



A slightly larger and somewhat different variety is represented bj' 

 Nos. 4701, 4715, 4732. 



Fig. II. Hyopsodus ■worimam'. Type. 

 Am. Mus. Cope, No. 4716. Superior and in- 

 ferior teeth. Twice natural size. 



3. Bridger (Bartonien) Stage. 



As shown in the chronological list above, six species 

 have been named from this formation and the synonomy can 

 only be cleared up by exact comparison of the types. Deuter- 

 ocones begin to appear on the second as well as the third and 

 fourth upper premolars; hypocones are still more prominent. 

 The Bridger specimens show a more or less decided external 

 cingulum in the upper molars. 



(Sp. 2) Hyopsodus paulus. — This includes the species of 

 middle size, inferior molars ==14 mm. With this should be 

 compared the type of (3) H. (Microsus) cuspidatus Leidy, 

 also of (16) Stenacodon rarus Marsh; also of (32) H. {Micro- 

 syops) vicarius Cope. 



