by Leidy in the Journ. Ac. Nat. Sci. Philad. ser. 2, vol. vii. 

 p. 403, pi. xxx. figs. 45, 46. 



Presented by Professor J. Leidy, 1876. 



47501. Cast of the greater portion of the mandible. The original 

 was obtained from the Eridger (Lower) Eocene of 

 "Wyoming, U.S.A., and is described and figured by Leidy 

 in the " Extinct Vertebrate Fauna of the Western Terri- 

 tories" (Rep. U.S. Geol. Surv. Terr.), p. 71, pi. v. figs. 1-3 

 (1H73), under the name of Troyosus castoridens, of which 

 it is the type. Presented by Professor J. Leidy, 1876. 



Family PLATYCHCEROPID^l. 



The type genus appears to the writer l to be closely allied to, if 

 not identical with, the North-American Esthonyx. The position of 

 the latter has been much discussed. It Was at one time placed by 



Fig. 2. 



Esthonyx burmeisteri, Copo. -The palate and mandible ; from the Wasatch 

 Eocene of Wyoming, U.S.A. |. a, lateral view of part of cranium and 

 mandible ; b, oral view of right half of palate ; c, oral view of mandible. 

 (From the ' Anier. Nat.') 



1 Geol. Mag. dec. 3, vol. ii. p. 360 ; see also p. 526 of the same. 



B2 



