414 THE PUERCO EPOCH. 



separate mandibular rami. The third and fourth superior premolars cover 

 a larger base than either of the true molars. The external cusp has a base 

 extended anteroposteriorly, but the apex is conical, and there are no basal 

 tubercles. The inner cusp has a crescentic base, as in Periptychus, but the 

 apex is narrowed and compressed conic. The external tubercles of the true 

 molars are subconic, and do not develop any external ridges. Thev are 

 connected by the crescentic slightly angular crest, or V, whose apex forms 

 the inner anterior boundary of the crown. This crest is not divided into 

 parts homologous with the intermediate tubercles. The crowns of the M. i, 

 ii, and iii are surrounded by a basal cingulum, which in the M. i develops 

 a tubercle at the anterior external angle. The posterior inner lobe is more 

 posterior in this species than in any of the others, and has a V-shaped 

 apex. It projects further inwards than the anterior inner lobe. It is repre- 

 sented by a mere tubercle of the cingulum in Mioclcenus. No internal or 

 external cingulum on Pm. iv. Enamel nearly smooth. 



The ranms of the mandible is rather slender anteriorly. The Pm. iv 

 is robust, and the cusp is above the middle of the base of the crown. Me- 

 dian anterior tubercle small, but distinct. The heel is short and narrow, 

 and has a raised border, connected with the base of the main cusp. Tlie 

 cusps of the true molars are elevated and conic, the anterior the highest, 

 and others subequal. The base of the posterior pair is a little narrower 

 than that of the anterior pair. There is no central tubercle as in Perip- 

 tychus rhahdodon, and no basal cingulum on any tooth. 



Diameters superior Pu.. iv \ ""teroposterior. 

 ( transverse 



Meusurements. 



M. 



Lcngtb of three superior molars 0160 



0055 



0070 



Diameters superior M.i J ""tcroposterior 0052 



( transverse 0060 



Length of inferior molar series 0010 



Length of inferior true inohir series 0160 



terior 0060 



0040 



Diameters inferior Pm. iv^ anteroposterio 



( transverse 



Diameters inferior M. ii $ anteroposterior IH.r.O 



( tninsverso 0040 



Depth ramus at M. ii 0090 



A number of minor points will distinguish this species from those 

 included among the Mesodonta, and also from those oi Pantolestes, whii-h it 



