HISTORY OF THE fCONDYLAKTHRA 457 



I. fMENISCOTHBRIID^. 



\Meniscotherium, Wasatch and Wind River. 



II. fPHENACODONTIDjE. 



■\ Protogonodon, Puerco. ^ Euprotogonia, Torrejon. \ Phenacodiis, 

 Wasatch and Wind River. 



1. ^Phenacodontidce 



The typical Wasatch genus \Phenacodus, which is very fully 

 known from nearly complete skeletons, included species which 

 varied in size from a fox to a small sheep ; the same genus 

 occurred in the Wind River, but not later. 'fPhenacodus 

 had the unreduced dental formula : i f , c y, p |, m |, X 2 = 44. 



Fig. 233. — Skeleton of the Wasatch toondylarth, ^Phenacodus primaemis. American 

 Museum. For restoration, see Fig. 141, p. 278. 



The incisors were small and simple, the canines tusk-like, 

 but of no very great size, the premolars smaller and simpler than 

 the molars. The latter were of the quadrituberculate pattern, 

 of four simple, conical cusps arranged in two pairs, a pattern 

 which is common to the earlier and less speciahzed members of 

 many ungulate groups. The skull was long, narrow and low, 

 with long and well-defined sagittal crest. As in primitive 

 skulls generally, the cranial region was long and the face short, 

 the eyes being very far forward ; this does not imply large 

 brain-capacity, indeed, the brain was very small, but merely 

 that the portion of the skuU behind the eyes was relatively 

 long. The jaws were short and shallow, in accordance with the 



