1 90 Bulletin American Museum of Natural History. [Vol. XVI, 



Family NOTHARCTIDiE Osborn. 



Limnotheridcs Marsh. 



The type genus, Limnotherium, is apparently preoccupied 

 by Notharctus Leidy; if not, LimnotheridcB takes precedence. 



Definition. — Upper incisors early reduced to |. Premolars persis- 

 tent, but with reduced fangs. Molars relatively low crowned and low 

 cusped; lower molars especially like those of many true Monkeys in 

 the broad depressed and early crenulate or tuberculate talonid. Para- 

 conid gradually reduced. External cusps of upper molars more cres- 

 centic than in Hyopsodus or Adapts, consequently developing a 

 nieso-style; also showing external cingulum. 



Unlike the Hyopsodontidae these animals show a pro- 

 gressive increase in size in as- 

 cending levels. This phylum 

 certainly includes the numerous 

 Wasatch and Wind River species 

 referred to Pelycodus [by Cope, 

 the Bridger species referred to 

 Notharctus and Hipposyus by 

 Leidy; to Hyopsodus (in part), 

 Limnotherium, Thinolestes, and 

 Telmatolestes by Marsh; to Pro- 

 totomus and Tomitherium by Cope. 

 The species Sinopa (Prosinopa) 

 eximia Leidy was based upon a 

 which should be compared with 



Fig. 18. Sinopa(Prosinopa)exi7nia. 

 Type. Phila. Acad. Twice natural 

 size. 



jaw contammg pg, p 

 Notharctus. 



To be compared with this family are the small animals, 

 Omom,ys carteri, Leidy ( ''i. ^, 

 c. Y, p. ^); and Hemiacodon 

 gracilis Marsh (^,t>7'3-). 

 true molars =11 mm. , molars 

 and premolars = 17.2 mm. 

 Also H. nanus Marsh, if. 

 pucillus Marsh ; the two species last named, however, should 

 also be compared with Anaptomorphus. 



Fig. ig. Oiiioiiiys carter!. Type. Superior 

 view of right ramus, traced from a photograph. 

 Twice natural size. 



