ANAPTOMORPHUS. 117 



or incisor tooth distinguishes it from both." (Cope.) C. LATI- 

 DENS, Cope, is the only species. 



GENUS OMOMYS. 



OmomySy Leidy, Journ. Acad. Nat. Sci. Philad., vii., p. 408 

 (1869). 



This genus was established for the first Mammalian fossil 

 a lower jaw described from the Bridger-beds as O. CARTERI. 

 The posterior lower molar has cusps in opposing pairs ; pre- 

 molars, three in number, the two anterior one-cusped, the 

 posterior two-cusped. The chin was longer and less rounded 

 than in Anaptowrphus, 



GENUS ANAPTOMORPHUS. 



Anaptomorphus, Cope, Proc. Amer. Phil. Soc., 1872, p. 554; 

 id., Rep. U. S. Geol. Surv., iii., p. 245, pi. xxiv. e, fig. i ; 

 xxv., fig. 10. 



This genus was founded by Cope on an almost entire cranium 

 discovered in the Bridger (Eocene) beds of the upper Valley of 

 Green river, and on other remains from what is known as the 

 Wasatch formation of the Big-Horn Basin in Wyoming Terri- 

 tory, in North America. The external upper incisor is small and 

 set close to the small canine ; the pre-molars have each a large 

 external and a smaller internal cusp ; the true molars are wide 

 and have one internal and two external cusps. In the lower 

 jaw the two anterior molars are four-cusped, with a trans- 

 verse ridge between the anterior pair, and an oblique ridge be- 

 tween the hind inner, and the front outer, cusp ; the posterior 

 is three-cusped and has a heel. The orbits are enclosed, as 

 in typical Lemurs. Not less typical characters are the position 

 of the lachrymal foramen, external to the orbit, and the un 

 ossified halves of the lowei jaw. " Its dental formula (If, 



