474 SINCLAIR— ENTELODONTS FROM THE 



tudinal section, concave proximally and convex distally. Trans- 

 versely, it is convex at the narrowest part of the process and sigmoid 

 toward the distal end, concave in front and convex behind. 



Fig. 6. Archceotherium wanlessi sp. nov. Holotype, No. 12522. Top view 

 of the skull, one sixth natural size. Drawn from photograph and the speci- 

 men. 



2. The structure of the zygomatic arch, used by Troxell as a 

 specific variant. At its narrowest part the arch is but 41 mm. wide 

 and the jugal process is slender, reaching the front margin of the 

 glenoid fossa, but not taking part therein. 



3. The character of the first lower premolar, which is said to be 

 small and single-rooted in A. marshi and large and double-rooted in 

 A. crassum. In A. wanlessi it has been lost on both sides and the 

 excavation of the alveolus fails to reveal any trace of a cross septum, 



