276 THE PUERCO FAUNA. 



u. 



Length baseof trae molars - 039 



Diameters baae of M.ii I ''°'"°P°^*"'°^ ^^'^ 



I transverse 021 



Diameters base, M. h; < anteroposterior 010 



( transverse 0175 



Elevation of base of zygoma above base of M. iii 018 



The ramus of the lower jaw is, as usually with the Creodonta, deeper 

 and less robust than that of Carnivora of corresponding size. It is also 

 more compressed than that of the Ty'iisodon quivirensis. It retains its depth 

 to below the canine teeth, and does not shallow below the middle of the 

 coronoid process, where also there is no tendency to inflection. The ante- 

 rior masseteric ridge is not very prominent, and the masseteric fossa is not 

 defined below, nor is the inferior edge of the ramus prominent or ridged at 

 that point. 



The premolar teeth are lost, but they occupied but a short space, and 

 were probably only three in number. The first and second true molai's are 

 subequal, while the third is a little smaller than either. Each consists of an 

 anterior higher and a posterior lower portion, the lower region being at the 

 junction of the two. The anterior part has a nearly circular section, and 

 contracts towards the apex. The latter is divided into three cusps, a larger 

 external and two lesser internal. The external and posterior internal soon 

 fuse on wearing, and their combined section is a crescent. The anterior 

 inner is small, and stands near the inner edge of the crown, and not at the 

 middle as in T. quivirensis, and is circular in section. The heel of the tooth 

 rises to its posterior border, which is divided into two cusps. Each of these 

 sends a ridge forwards towards the base of the anterior cone of the tooth. 

 The external is the larger, and reaches that base. The internal is smaller, 

 and falls short of it. The posterior inferior molar differs from the others in 

 form as well as in size. There is no posterior inner anterior cusp, the large 

 external cusp being supplemented by a small anterior internal only, which 

 sends a little ridge downwards and posteriorly. The heel is narrowed, and 

 supports the two cusps on its posterior border in contact, and not separate 

 as on the other teeth. The external is the larger, and extends forwards to 

 the base of the anterior cone near its middle. Some remnants of hard 

 matrix leave it uncertain whether there is a small median posterior marginal 

 tubercle on the first and second molars or not 



