E. L. Troxell — Entelodonts in Marsh Collection. 361 



Art. XXIV. — Entelodonts in the Marsh Collection; by 

 Edward Lefeingwell Troxell. 



[Continued from p. 255.] 



PART II. THE GENUS ARCHCEOTHERIUM. 



Generic Characters of Archceotherium Leidy. 



Archceotherium ranges in size from that of A. clavus 

 to that of A. eras sum; the known species are limited to the 

 Oligocene, generally Lower or Middle. As distingnished 

 from Entelodon Aymard, it has longer diastemata sepa- 

 rating the premolars ; premolars more primitive in having 

 double roots (exception: P 3 of A. marshi, sp. nov.) and 

 less primitive in their small size and the consequent 

 greater separation; P 3 not so wide posteriorly; P 4 not 

 quadrate but invariably with a notch on its anterior face ; 

 anterior cusps of the lower molars higher than those pos- 

 terior. (As to the skull, one finds great difficulty in ac- 

 cepting the published reproductions of the cranium of 

 Entelodon magnus as trustworthy evidence of the very 

 unusual features represented.) 



As distinguished from Pelonax Cope, the chief features 

 of Archceotherium are the generally double-rooted premo- 

 lars, the smaller size of the mental tubercles, and the much 

 smaller size of the animal as a whole. As distinguished 

 from Dinohyus, medium incisor never known to be absent ; 

 P 3 always much longer than wide, anterior and posterior 

 cones unequal in lower molars ; dependent process gener- 

 ally large, posterior end of malar bone may end before the 

 glenoid cavity; processes may be relatively large on chin, 

 and the generally long chin and long premaxillary have 

 the incisors separated. Dinohyus is, moreover, twice as 

 large as the smallest species of Archceotherium and is 

 known only from the Lower Miocene. 



Archceotherium clavus Group. 

 Archceotherium clavus (Marsh). 



Holotype, Cat. No. 12035, Y. P. M. Middle Oligocene, White Kiver, 

 Nebraska. 



Following is the original description of this species 

 (Marsh 1893, p. 409). 



