NO. 7 MAMMALIA FROM THE ALMY FORMATION GAZIN 5 



(U.S.N.M. No. 16696), a right mandibular ramus with P3-M2, but 

 lacking the trigonid of Mi, and a left M^ tentatively referred to 

 Plesiadapis riiheyi. 



P. rubeyi clearly belongs to the group of species that includes 

 P. gidleyi, P. fodinahis, P. dubius, and probably P. cookei. It is 

 remote from the distinctive P. jepseni-P. anceps-P. rex group or 

 subgenus. It is, moreover, rather close to P. fodinatus which Jepsen 

 ( 1930) described from the Silver Coulee horizon of the Polecat Bench 

 sequence. There is a possibility that P. rubeyi is not specifically dis- 

 tinct from P. fodhiatus; however, in view of the distinctly small size 

 of Ml, the anteroposteriorly shorter appearing summit of the trigonid 

 of IM2, and the comparatively slender premolars showing an incipient 

 metaconid on P4 (as in P. dubius rather than P. fodinatus), the 

 species P. rubeyi would seem to be valid. Moreover, P. fodinatus is 

 typically Tiffanian in age, regarded as represented in the Bison Basin 

 deposits and Fossil Basin Evanston(?) as well as in the Polecat 

 Bench, and survival of this species into Clarkforkian time, though 

 likely, awaits demonstration. 



The tentatively referred last upper molar (U.S.N.M. No. 16697) 

 is distinctly large for the type lower jaw of P. rubeyi and is postero- 

 lingually expanded somewhat as in P. fodinatus. It is possible that 

 this tooth represents P. fodinatus, but the evidence is rather meager 

 and would not seem to justify separate listing. The tooth measures 

 4.3 mm. anteroposteriorly by 6.0 for the greatest transverse diameter. 



MEASUREMENTS IN MILLIMETERS OF LOWER TEETH IN TYPE SPECIMEN OF 



Plcsiadapis rubeyi, u.s.n.m. no. 16696 



Ps, anteroposterior diameter : transverse diameter 2.8: 1.9 



P4, anteroposterior diameter : transverse diameter 2.9 : 2.2 



Ml, transverse diameter of talonid 2.7 



Ml, anteroposterior diameter : transverse diameter of talonid 3-7 '• 3-2 



PLESIADAPIS COOKEI Jepsen, 1930 



Plate I, figures 5-8 



In addition to the lower jaw of Plesiadapis cookei (U.S.N.M. 

 No. 16698) found in 1941, a second lower jaw with all three molars 

 and an isolated M^ were found by Franklin Pearce while in the field 

 with me in 1954. Plesiadapis cookei is truly gigantic in comparison 

 with other Paleocene primates and is nearly as large as the upper 

 Bridgerian Notharctus robustior. Direct comparison of these jaw 

 materials with the type specimen in the collections of Princeton Uni- 

 versity shows near identity in size and character of the teeth for the 



