HATCHER : OLIGOCENE CANIDJE 99 



most important resemblances between the present genus and Amphicyon are to be 

 found in the dentition and have already been noticed. These may be recapitulated 

 as follows : 



First: Canine elliptical in cross-section or flattene 1 transversely an 1 with pos- 

 terior cutting edge. 



Second: Premolars J-.-^--^- much reduced in size. 



Third: Superior sectorial long and narrow. 



Fourth : Molars i^ much expanded transversely. 



Fifth: Molar -^ large, as indicated by presence of two alveoli, and aligned with 

 external border of M. i^. 



The cranial characters of the American species of Amphicyon are not sufficiently 

 well known to permit of a comparsion of these characters in the two forms. Judg- 

 ing from the dental characters alone however the present genus would appear to 

 fulfill all the requirements that we might reasonably except to find in a White 

 River ancestor of the Miocene form, except that P.-- -> - are perhaps a trifle too much 

 reduced in size. I therefore for the present regard Proamphicyon nebrascensis as 

 ancestral to Amphicyon americanus. 



PROTEMNOCYON INFLATUS, gen. et sp. no v., Plate XV. 



Among the material collected by Mr. Peterson is a beautifully preserved skull 

 (No. 552) with lower jaw, for which, from its evident relation to Temnocyon, I pro- 

 pose the genus Protemnocyon. In reference to the capacious nature of the brain 

 cavity it is proposed to designate the species as P. inflatus. 



Char. Gen. — Sagittal crest very low throughout the anterior two thirds of its 

 length. Brain-cavity much inflated, indicating a brain one half larger in proportion 

 to the size of the skull than that of Daphoenus or Proamphicyon. Dental formula, 

 I.f, C.\, P.f, M. f-^. Heel of inferior sectorial and M.o imperfectly keeled. 



Char. sp. — Temporal constriction anterior to union of superciliary ridges. Fron- 

 tals broad, gently concave medially, but convex laterally, indicating the presence 

 of well-developed frontal sinuses. Inferior margin of mandible nearly straight. 

 M.-^ much reduced in size or absent. F.\, |, f , j large and with broad heels. 



Detailed Description of Type (No. 552). 



The type of Protemnocyon inflatus consists of a skull with lower jaw, atlas, axis, 

 and third cervical found in position in the Oreodon beds on Bad Land Creek, Sioux 

 Co., Neb. 



