58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



example, A. minimus. The tetartocone is actually more advanced and 

 rather more Agriochoerus-like in certain specimens of P. pumilus. 

 A particularly advanced tetartocone on P* was noted in a specimen 

 from the Uinta C of Leland Bench draw (U.S.N.M. No. 20449). 



Not all the protoreodont specimens from the Duchesne River beds, 

 or attributed to the Beaver Divide conglomerate, are to be referred 

 to P. primus, as the specimen (CM. No. 12080) from near Baser 

 Bend in the Uinta Basin, which Scott (1945, p. 233) referred to this 

 species is, I believe, closer to Protoreodon pumilus annectens in the 

 premolars. The specimen (A.M. No. 22558) purported to be from 

 the Beaver Divide conglomerate, which Scott also included in this 

 species, is rather immature and exhibits no permanent premolars. 

 The molars in this are typically protoreodont with distinctly selenodont 

 cusps, very distinct protoconules, and a size close to P. pumilus. The 

 species represented is not clearly evident. The type of Protoreodon 

 tardus is also stated to be from the Beaver Divide conglomerate. The 

 differences between molars of it and A.M. No. 22558 are slight, but 

 the P. tardus type strangely enough would appear to be closer to 

 Protoreodon pumilus ss. than to P. primus. 



MEASUItEMENTS IN MILLIMETERS OF DENTITION IN TYPE SPEaMEN OF 



Protoreodon primus, cm. no. 11893 



Length of upper cheek tooth series, C (at alveolus) -M", inclusive. . . 73-^0' 



Length of upper cheek tooth series, P*-M^ inclusive 64.3a 



Upper premolar series, P^-P*, inclusive 32.8 



Upper molar series, M^-M', inclusive 33.0a 



C, anteroposterior diameter 6.0a 



PS anteroposterior diameter : greatest transverse diameter 6.8 : 3.0a 



P^ anteroposterior diameter : greatest transverse diameter 8.8 : 3.9 



PS anteroposterior diameter : transverse diameter* 8.3 : 6.2 



P*, anteroposterior diameter : transverse diameter 7.5 : 8.8 



MS anteroposterior diameter : transverse diameter* 9.4a : 9.60 



MS anteroposterior diameter : transverse diameter 10.6 : 12.5a 



Length of lower cheek tooth series, Pi (at alveolus) -Ma, inclusive. . 70.0a 



Lower premolar series, Pi (at alveolus)-P4, inclusive 34.4 



Lower molar series, M1-M3, inclusive 35-50 



Pi, anteroposterior diameter : greatest transverse diameter 7.0 : 4.5 



P2, anteroposterior diameter : greatest transverse diameter 7.9 : 3.2 



Pa, anteroposterior diameter : greatest transverse diameter 8.S : 3.7 



P4, anteroposterior diameter : greatest transverse diameter 9.2 : 4.7 



Ml, anteroposterior diameter : transverse diameter of talonid 8.3 : 6.2 



Ma, anteroposterior diameter : transverse diameter of talonid 10.60 : . . . 



Ms, anteroposterior diameter : transverse diameter of trigonid 16.00 : 7.8a 



a. Approximate. 



* Measurements of posterior upper premolars are taken anteroposteriorly across outer por- 

 tion and transversely perpendicular to outer margin. Those of upper molars are talcen 

 anteroposteriorly perpendicular to anterior margin and transversely across anterior portion 

 of tooth. 



