ANAPTOMORPHUS. DI7 
or incisor tooth distinguishes, it from both.” (Cope.) C. Lari- 
DENS, Cope, is the only species. 
GENUS OMOMYS. 
Omomys, 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 Anaptomorphus. 
GENUS ANAPTOMORPHUS. 
Anaptomorphus, Cope, Proc. Amer. Phil. Soc., 1872, p. 554; 
idee. Oo, GrcOl, SUV. Ill. Pp. 245, pl xxlys e, foe Tr ; 
Xxv., fig. Io. 
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 Wycming 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 lowe: jaw. ‘Its dental formula (13, 
