22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



MEASUREMENTS IN MILLIMETERS OF LOWER TEETH IN SPECIMENS OF 



Pronothodectes simpsoni 



U.S.N.M. 



No. 207S4 U.S.N.M. U. of Wyo. 



(type) No. 20770 No. 1057 * 



Length of lower molar series 9.8 8.9 9.4 



P4, anteroposterior diameter : transverse 



diameter 2.5 : 1.9 2.2 : 2.0 



Ml, anteroposterior diameter : greatest 



transverse diameter 2.8 : 2.4 2.6 : 2.3 2.5 : 2.1 



Ma, anteroposterior diameter : greatest 



transverse diameter 3.1 : 2.8 2.9 : 2.5 2.7 : 2.5 



M3, anteroposterior diameter : greatest 



transverse diameter 4.3 : 2.5 3.6 : 2.2 4.4 :• . 



* Small variant but with large M3 



PLESIADAPIS, cf. FODINATUS Jepsen, 1930 

 Plate 2, figure 3 



Three specimens in the collections of the National Museum and 

 three in those of the University of Wyoming are believed to repre- 

 sent the comparatively large plesiadapid that Jepsen (1940) described 

 from the Silver Coulee horizon in the Polecat Bench series of north- 

 western Wyoming. Represented among these are P4 to M3, and only 

 one (U. of Wyo. No. 1085) of the specimens is a maxilla, exhibiting 

 M2 and M3. The specimens, with one exception, are from the more 

 westerly localities and probably higher stratigraphically than the sad- 

 dle locality and possibly higher than the ledge. One jaw with teeth 

 a trifle smaller than in the others came from the ledge but is believed 

 to be closer to Plesiadapis fodinatus than it is to the new form, 

 P. jepseni. 



The teeth in the Bison basin materials referred to P. jodinatus cor- 

 respond so closely to those of the Silver Coulee form that there would 

 seem to be no serious doubt as to the correctness of the assignment. 

 The resemblance is very close in all proportions of the molar teeth, 

 and like P. jodinatus the teeth do not show such markedly sloping 

 labial walls as in correspondingly large Plesiadapis rex and related 

 P. anceps. It was noted, however, that in one of the jaws, which has 

 preserved the alveoli of the anterior cheek teeth, a small P2 had been 

 present, although there was no evidence of a Pi. P2 is not present in 

 the type or other observed materials of P. jodinatus from the Prince- 

 ton Quarry but is present in P. gtdleyi and almost always present, 

 though not invariably so, in the material described below as the new 

 species, Plesiadapis jepseni. Its presence in the Bison basin jaw com- 

 pared with P. fodinatus may not be significant. There is, moreover, a 

 suggestion in this particular jaw of somewhat smaller premolars and a 



