196 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



Table 40. — Individual measurements (in mm) of Prothryptacodon furens 



FiGURK 45. — Prothryptacodon furens Simpson, U.S.N.M. no. 9260, right lower jaw: a. Crown view; 6, 

 internal view. Twice natural size. 



Figure i6.—Chriacus pugnax Simpson, U.S.N.M. no. 13782, right lower jaw, crown view. Twice natura 



size. 



Genus CHRIACUS Cope, 1883 



This genus typifies the Torrejon but has been reported also in the 

 Puerco and in the Almagre. It is improbable that a single genus had 

 this enormous, almost unique length of distribution, and the earliest 

 and latest forms, known only from fragments, may well prove to be 

 distinct. The pattern is a simple and generalized one, easily confused 

 with that of allied forms, and requiring close study and good material 

 for its certain distinction. 



The appearance of Chriacus in the present fauna would be expected, 

 from its age relationships, and this genus was reported by Douglass 

 (1908) and by me (1935d). The earlier reports, howeve/ now prove to 

 be doubtful or erroneous. As elsewhere noted, one species hitherto 

 referred to Chriacus is now placed in Metachriacus. The other, 

 C. pugnax, is retained here, but the specimen on which it is based is so 

 incomplete that the generic reference is not certain. 



