16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



MEASUREMENTS IN MILLIMETERS OF CERTAIN LOWER TEETH IN JAWS OF 



Phenacodus 



p. ahnii^nsis 

 U.S.N.M. 

 No. 20643 



P4, anteroposterior diameter 9.6 



P4, transverse diameter of talonid 6.2 



Ml, anteroposterior diameter 9.1 



Ml, transverse diameter of talonid.... 7.4 



M2, anteroposterior diameter 



M2, transverse diameter of trigonid 



" Approximate. 



DINOCERATA 

 UINTATHERIIDAE 



PROBATHYOPSIS?, sp. 

 Plate I, figures 2 and 3 



Two upper premolars, possibly both P^, or P^ and P*, but of differ- 

 ent individuals as indicated by wear, are evidently of Probathyopsis. 

 They are, however, significantly larger than Probathyopsis praecursor 

 Simpson (1929) of the Clark Fork beds. They correspond closely in 

 size to a P^ belonging with a partial skeleton of cf. Bathyopsis flssi- 

 dens Cope from the New Fork upper Wasatchian (Gazin, 1952, 

 p. 64), but are slightly more brachydont. The unworn Almy premolar 

 (U.S.N.M. No. 21283) measures 14.6 mm. long perpendicular to 

 anterior margin by 16.5 mm. wide perpendicular to outer wall. P' in 

 the type of P. praecursor measures 11.5 by 13.3 mm. in the same 

 directions. 



The proportions of the upper premolars are comparable to those of 

 the earlier Bathyopsoides harrisorum Patterson (1939) from the 

 Plateau Valley beds, although the unworn Almy premolar is a little 

 shorter anteroposteriorly and broader transversely than the B. harris- 

 orum P^. Nevertheless, the transverse lophs have about the same 

 proportions. Although Patterson has indicated certain differences in 

 cusp pattern of M2, it would seem from the evidence presented by 

 Dorr (1952, p. 89) that Bathyopsoides is possibly a male Probath- 

 yopsis. Better evidence with regard to this situation should be forth- 

 coming in the more detailed study of the Hoback Basin material 

 contemplated by Dorr. 



