224 



and the shallow wide symphyseal surface is divided by a deep groove from the 

 outer side, into which opens the mental foramen. Tlierc are two external planes 

 of the dentary : the superioi-, or narrower, supporting the teeth, is bounded 

 by a shallow groove below; the inferior and deeper plane terminates in a 

 free, thin edge, excepting near the symphysis, where it is a little thickened, 

 and stands at an angle of 45° with the symphyseal surface. 



The dentary is deeply doubly emarginate posteriorly, to receive the 

 large angular ; the upper emargination is in the superior plane, the inferior 

 in the inferior, and the ramus is deepest at the fundus of the notcii. From the 

 two posterior ajnces, the ramus contracts gradually, the inferior border to the 

 end of the long oval angle, the superior outline abruptly to the cotylus. The 

 upper plane behind the upper emargination is occupied by a large longitudi- 

 nally-oval fossa. A dentary, from which about an inch has been broken from 

 the posterior upper end, supports thirty teeth, with one on the symphysis 

 within the anterior one. From their reduced size, I suspect that the posterior 

 teeth of the specimen were not followed by others. The crowns are conic, 

 without cutting-edges, with smooth enamel, and strongly incurved. 



Measurements of No. 1. 



M. 



Longtli of tlio niau(lil)nlar ramus 0.305 



Deptb of tho mandibular ramus at tlio last tooth 0. 060 



Dcptli at tbo corouoid angle 0. OC) 



Depth at the cotylus 0.019 



Width of the syuiphysis .' 0.022 



Length of the crown of a tooth 0.009 



Length of tho root of a tooth 0.010 



Length of the hyomandibular bone 0. 074 



This species is about the same size as the P. caninus. The coronoid 

 angle of the mandible is elevated above the cotylus 45™" ; in P. caninus, of 

 the same size, 25°"°. 



In the second specimen, the general form apjjears to have been deeper 

 tliaii in the P. caninus, while the size of the teeth is similar. The external 

 face of the bone near the alveolar border is convex, and not particularly 

 rugose. The external alveolar wall is well elevated above the inner. IJelow 

 the latter, the dentary bone exhibits a strong longitudinal ridge. The 

 extremity of the dentary takes u wider curve from the symphysis than in 

 P. caninus, giving a broader chin (whence the name) and muzzle. The 

 symphyseal surface is smooth, transverse trilobate; the two outer lobes being 

 separated by an emargination in the position of the foramen mentale. This 



