HYJEXODONTIDJE. 35 



specimen is referred to the present genus on the authority 

 of Bravard. Bravard Collection. Purchased, 1852. 



28163-4. Three lower premolars 1 of small size, not improbably 

 belonging to a small race of the present species ; from the 

 Upper Eocene of Vaucluse. 



Bravard Collection. Purchased, 1852. 



28154. Cast of a portion of the right ramus of the mandible, showing 

 the last three premolars : the original is from the Tipper 

 Eocene of Yaucluse. Bravard Collection. Purchased, 1852. 



M. 1719. Fragment of the left ramus of the mandible of a large- 

 sized individual, containing the two last molars ; and a 

 fragment of the anterior part of a ramus with two worn 

 teeth ; from the Upper Eocene of Bach. Purchased, 1884. 



Genus OXY-ffiNA, Cope 2 . 



This genus is apparently distinguished from Pterodon merely by 

 the absence of the third molars in both jaws, and by the diminu- 

 tion in the number of the incisors. Since one species of Pterodon 

 (P. biincisivus) has only two pairs of incisors in the upper jaw, and 

 possibly only the same number in the mandible, there is a transition 

 in this respect towards the present genus ; and as the only other 

 distinction is the absence of the last true molars, the writer is 

 strongly inclined to think that Oxycena might be merged in Pterodon. 

 The following formula 3 represents the range of variation in the 

 number of teeth of Oxycena, viz. I. ( ^f>, C. \, Pm. |, M. f. 



Oxysena gallise, Filhol 4 . 



Dentition : I. ?, C. \, Pm. \, M. |. Filhol founded this species 

 on a fragment of the maxilla in which the incisors were not shown. 

 He was not, therefore, aware that these teeth were only two in 

 number, in place of three, as in the American species. 



Hob. France. 



1 Entered in the Museum Eegister as P. aymardi, Bravard, MS. 



2 Report U.S. Geogr. Surv. W. of 100th Meridian,1874, p. 11. Vert. FOBS. New 

 Mexico. 



3 In his latest notice (Amer. Nat. 1884, p. 480) Cope gives the number of 

 cheek-teeth as Pm. f, M. f . The figure of the upper dentition given on the 

 opposite page of his memoir shows, however, that this is incorrect. 



* Ann. Soc. Sci. Phys. Nat. Toulouse, 1882, p. 3i. 



D2 



