the Marsh Collection. 



393 



of the double internal crescent described by Matthew in 

 Pseudolahis dakotensis, although by no means so well 

 developed. 



Compared with its contemporary from the Protoceras 

 beds, Pseudolahis dakotensis, the present species resem- 

 bles the latter in the comparable cranial details, the rela- 

 tive spacing of the anterior teeth, the character of the 

 third and fourth premolars, and in the actual size of J\P. 

 It differs from Matthew's form in the smaller size, more 

 attenuated muzzle, relatively larger C^ and P, and rela- 



W767. TYPE 

 Y. p. M. 



Fig. 1. — Fseudolabis (Parala'bis) matthewi, subgen. et sp. nov. Holotype. 

 Palatal aspect. A little less than one half nat. size. 



tively much smaller premolars, as the table of measure- 

 ments shows. The presence of the mesostyle, absent in 

 the molars of P. dalcotensis, is also very distinctive. 

 Some of these distinctions, as, for instance, the relatively 

 smaller canine and P in P. dakotensis^ might be sexual, 

 were their possessor not a considerably larger animal. 

 The presence of the mesostyle and the relatively more 

 elongate muzzle and smaller premolars of the new form 

 are both progressive characters which its contemporary 

 lacks, showing the two to be divergent species, as the time 

 and space limitations render the derivation of one from 

 the other impossible. The gap so formed between them 

 is certainly of subgeneric and possibly of generic rank. 



The present form differs from P o eh r other imn in the 

 larger size, the character of the auditory bullae, the more 

 prominent mesostyles, the relatively larger and more 

 caniniform P, and the more attenuated muzzle, with, as 

 a consequence, the longer diastemata, especially between 

 the canine and P^. "Wliether or not the rear of the orbit 

 would prove a contrasting character can not be shown in 

 the present specimen. In the type of Pseudolahis dako- 



