364 E-. L. Troxell — Entelodonts in Marsh Collection. 



the lachrymal, approximately square, is high in front of 

 the orbit. The jugal occupies a very small area on the 

 face ; on the other hand the maxillary forms no part of the 

 arch anteriorly. The vertical position of the orbit is very 

 similar in all the species ; its anterior edge lies over the 

 metacone of M 2 . 



The upper incisor teeth are pyramidal or subtetrahe- 

 dral, recurved and slender. They are slightly flattened, 

 with sharp corners postero-externally and antero-inter- 

 nally. The upper canine, already slender and long, is 

 worn on the anterior side in such a way as to emphasize 

 its slenderness. It is recurved. 



P 1 is situated very near, in fact, fairly beside the canine, 

 and therefore assumes a diagonal position. Though 



Fig. 3. — Arc'hceotlierium clavus clavus (Marsh). Holotype. Cat. No. 

 12035. Crown view of (A) upper, and (B) lower teeth. One-half nat. size. 



small, it is as large as those found in much larger species. 

 P 2 is relatively large, is well separated from P 1 , but is 

 close to P 3 . 



A noticeable thing about the third upper premolar is its 

 concavity internally, and as a consequence the wider pos- 

 terior heel, which gives the tooth an unusual thickness, 

 15.4 mm. Both fore and aft are developed cingular edges. 

 A serrated fold runs to the point of the cone, and the heel 

 is very rough. It not only has the platform mentioned 

 by Leidy, but also a cingulum back of that. Postero-in- 

 ternally is a roughened area bordered by ridges running 

 vertically. The third premolar joins the fourth without 

 a diastema. 



P 4 , implanted 'with three fangs, is much more molari- 

 f orm, but is composed of two cusps only. The outer cone, 

 or protocone, which may really be the protocone and trito- 

 cone combined, is considerably stronger and points 





