FORT U:N^IO]Sr OF CRAZY LIOUNTAIN FIELD, MONT. 



123 



Diagnosis. — P4 and M2-3 significantly larger than in B. thomsoni, Mi 

 about same size. Heel of P4 relatively larger, talonid of M3 more 

 elongate. Amphicone of P* more compressed. 



Remarks. — The dentition is closely similar to that of B. thomsoni, 

 fully described elsewhere (Simpson, 1936b). 



Table 26. — Dentition measurements (in mm) of Bessoecetor diluculi 



Figure 21.— Bessoecetor 

 dilaculi (Simpson), U.S. 

 N.M. no. 9553, with part 

 in outline added from 

 U.S.N.M. no. 9585, left 

 upper jaw: a, External 

 view; 6, crown view. 

 Three times natural size. 



Figure 22.— Aphronorus fraudator Simpson, U.S. 

 N.M. no. 6177, left lower jaw: a. Crown view; 6, 

 external view. Three times natural size. 



Pentacodontinae, new subfamily 



Type. — Pentacodon Scott, 1892. 



Distribution. — Middle Paleocene (and doubtfully Upper Paleocene), 

 North America. 



Diagnosis. — P^ much enlarged. P4 with very heavy protoconid, 

 sloping backward, well-developed metaconid, and basined heel. P* 

 with massive, conical, paracone, smaller but sharply distinct metacone, 



