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University of California . 



[Vol. 3. 



smaller than the one behind it. The root of exhibits a deep 

 groove near the top and was probably divided toward the lower 

 end. The molariform crown seems to be somewhat worn but 

 the button-like base is very thick, with a transverse diameter 

 almost equalling the longitudinal. Pt has nearly two and one 

 half times the antero-posterior extent of Pa. The simple cone 

 of the crown has no anterior or posterior accessory tubercles, 

 although there is a shelf on the cingulum at the posterior inner 

 angle. On both rami the crown of this tooth is bent backward 

 slightly and is very close to the anterior blade of the carnassial. 



In the molar series, Mt is exceedingly massive and with Pt 

 has done practically all of the work falling to the cheek teeth. 

 The protoconid and paraconid are both greatly developed. No 

 trace of a metaconid is discovered, although the postero-internal 

 ridge of the protocone is prominent. The small talonid supports 

 an external and an internal tubercle, both of which are very 

 small and low. The crown of M2 bears an anterior and a poste- 

 rior tubercle, of which that representing the talonid is much the 

 smaller. M/t is represented by a small alveolus on each ramus. 



Affinities. — The dentition of Hyaenognathus has a striking 

 resemblance to so much as is known of the problematical genus 

 Borophagus, described from a jaw fragment found in the Blanco 

 beds of Texas. For comparison Cope's figures* of the type spec- 

 imen are reproduced here together with outlines of the correspond- 

 ing portion of the Hyaenognathus jaw (figs. 1, 2, 3, 4, 5). The 

 only other specimens referred to Borophagus are an inferior pre- 

 molar with a conic basal cusp and a single blade of a sectorial, 

 which were thought by Cope to belong here. If the premolar with 

 a conic basal cusp belongs to Borophagus, the Californian form 

 could not be closely related to this genus. If this is eliminated 

 as doubtful and a comparison made with the type, we find the two 

 forms possessing a combination of characters not found elsewhere. 

 Both have the reduced Pit, depressed Pa, and the greatly 

 enlarged, simple Pt. Cope's restorations of Pt in fig. 2 and 

 fig. 4 show the posterior basal lobe of this tooth considerably 

 extended. According to his view of the tooth in fig. 5, this 



*Geol. Surv. Texas, 4th Ann. Rep., 1892. Vert. Palaeont. Llano Estac. p. 52, 

 PI. XIII, figs. 4, 4a, 46. 



