184 Bulletin American Museum of Natural History. [Vol. XVI, 



(Sp. 5.3) Hyopsodus powellianus Cope. — Measurements 

 of three inferior molars in the type: 18 mm. This includes 

 the robust jaws and teeth, namely, Am. Mus. Coll., the type 

 No. 4147, and Nos. 4148, 4150, 4151, 4152. These are as 

 large as, or larger than, the largest species known from the 

 Bridger; the mj - mg = 16 to 18 mm. 



(Sp. 50) ? Hyopsodus (Diacodexis) laticuneus resembles 



Fig. g. Hyopsodus pozuellianus. Am. 

 Mus. No. 4147. Slightly less than twice 

 natural size. 



Fig. 10. Diacodexis laticuneus. 

 Type. Am. Mus. No. 4202. Twice 

 natural size. 



this species in size but differs in the presence of a paraconid. 

 This type is, however, of uncertain reference. 



Dr. Matthew has observed that these species may be ar- 

 ranged in three groups, including larger and smaller jaws in 

 each group, which may represent successive stages of develop- 

 ment in a long geological age ; these differences of size may 

 however represent males and females respectively. 



2. Wind River (Lutetien) Stage. 



Common characters of the Wind River species. — Hyopsodus 

 is represented by a large number of specimens from the Wind 

 River beds which Cope mistakenly referred to the Bridger 

 species H. paidus and H. vicarius. The superior molar teeth 



