NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 51 



Slight changes noted in the cheek teeth of P. pumilus are apparently 

 to be correlated with time. It is interesting to note that most of the 

 Protoreodon dentitions from the Protylopus quarry and vicinity in 

 Myton pocket tend to resemble the type of "Protagriochoerus" an- 

 nectens somewhat more closely than that of P. pumilus. This is noted 

 in an average larger size and almost imperceptibly more selenodont 

 outer cusps of lower molars as compared with materials obtained from 

 Leland Bench draw, I am convinced that the level from which fossil 

 material was collected along Leland Bench draw is a little earlier in 

 Uinta C time than the quarry in Myton pocket, and that the type of 

 P. pumilus which these materials closely resemble is from low in "C," 

 which would be in keeping with the locality designation "White 

 River" on the Marsh specimen. 



In view of the average difference between specimens in the collec- 

 tion noted above, I am tentatively designating the more-advanced ma- 

 terial, including much of that from Myton pocket, as the subspecies 

 Protoreodon pumilus annectens. 



The size of the caniniform teeth in P. pumilus is clearly not to be 

 correlated with size or other characters of the cheek teeth. Large 

 and small upper canines and lower Pi's are to be found in individuals 

 grouped according to size and development of cheek teeth. There does 

 appear, however, to be correlation between caniniform tooth size and 

 the extent to which the angle is expanded posteriorly, together with 

 the somewhat more posterior placement of the condyle, and to a minor 

 degree the depth of the ramus generally. The latter variables are in 

 part, of course, a function of the age of the individual as determined 

 by wear on the cheek teeth. Specimens can be readily divided into 

 two groups where preservation includes the upper canine or Pi, but 

 I have been unable to make this same separation on the basis of the 

 cheek teeth alone. I cannot regard the differences here cited as of 

 more than dimorphic significance within the species of P. pumilus. 

 It may be further noted that in those individuals which I regard as 

 males, a slightly greater diastema developed posterior to the large C. 



MEASUREMENTS IN MILLIMETERS OF DENTITIONS IN SPECIMENS OF 



Protoreodon pumilus 



A.M.!" U.S.N.M. 



No. No. 



1818 20352 

 Length of upper cheek tooth series, C (at alveolus )-M^ 



inclusive 81.5 76.0a 



Length of upper cheek tooth series, P*-M', inclusive 70.70 69.3 



Upper premolar series, P^-P*, inclusive 36.4a 35.O 



2* Type of "Protagriochoerus" annectens. 



