26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



the dozen or more other specimens of T. jremontensis at hand the 

 relative narrowness of the anterior molars, particularly the trigonid 

 of Ml, may be distinctive. The type, U.S.N.M. No. 20582, is a com- 

 paratively large individual with teeth relatively wider than nearly all 

 others from this locality. Their width, however, in proportion to their 

 length (more evident in Mi), though matched in certain individuals of 

 T. subtrigonus, is rather less than the average in the Torrejon ma- 

 terials observed. Other specimens of T. jremontensis appear to be 

 outside the range of T. subtrigonus in this respect. Moreover, the 

 paraconid on M2 and M3 is placed low on the trigonid of lower molars 

 in T. jremontensis and is weaker than generally seen in T. subtri- 

 gonus. In none of the posterior lower molars of the Bison basin form 

 is this cusp so conspicuously developed as it is in so much of the 

 Torrejon material. It should be noted, however, that the difference 

 is one in average for the material at hand, as teeth of T. subtrigonus 

 can be found in which there is scarcely a trace of the paraconid on M3. 



MEASUREMENTS IN MILLIMETERS OF TEETH IN SPECIMENS OF 



Triccntcs jremontensis 



U.S.N.M. 

 No. 20584 



Ps, anteroposterior diameter : transverse diameter 4.0 : 2.4 



P4, anteroposterior diameter : transverse diameter 4.5 : 2.9 



U.S.N.M. 



No. 20582 



(type) 



Ml, anteroposterior diameter : transverse diameter of trigonid 6.2:3.8 



Ml, transverse diameter of talonid 4.5 



Ma, anteroposterior diameter : greatest transverse diameter 6.4 : 4.9 



Ms, anteroposterior diameter : greatest transverse diameter 6.6:4.3 



CHRIACUS, near C. PELVIDENS (Cope), 1881 



Plate 5, figures i, 2 



About four fragmentary jaws of a species of Chriacus are included 

 in the collections of the National Museum. Unfortunately, only one 

 of these (U.S.N.M. No. 20983) has as many as two complete teeth. 

 The form represented is undoubtedly close to Chriacus pelvidens of 

 the Torrejon, with the anteroposterior diameter of the lower teeth 

 about the same as in that species. Their width, however, in two of 

 these is a little greater than in any of the C. pelvidens material at 

 hand. Moreover, the metaconid on P4, in one of the two specimens 

 that retains this tooth, is distinctly better developed, as it is in small 

 Spanoxyodon latruncidus. Although a distinct species of Chriacus, 

 or even possibly Spanoxyodon, may well be represented here, the evi- 

 dence is not conclusive and no satisfactory diagnosis can be made. 



