50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



Protoreodon pumihts is clearly the best represented species of 

 Protoreodon, and its remains are by all odds the most frequently 

 encountered in the Myton fauna. Much individual variation is noticed 

 in size, details of the cheek teeth, and development of canines. The 

 extremes in most details are rather well represented by the types of 

 P. pumilus and "Protagriochoerus" annectens, and the latter might 

 well be regarded as a variant, or mutation in time, and would have 

 been recognized as a separate species were it not for the mass of 

 material intervening. Protagriochoerus is not a valid genus, as Peter- 

 son (1919, p. 88) fully appreciated, and at the same time there ap- 

 pears to be no justification for Peterson's Protoreodon medius, which 

 corresponds rather closely to the type of "Protagriochoerus" annec- 

 tens. The greater selenodonty of the outer cusps of the upper molars 

 noted by Scott as characterizing Protagriochoerus was evidently a 

 comparison made with the type of Protoreodon parvus, which must 

 surely be from Uinta B. The significance of this, however, on a ge- 

 neric level, is lost in the intervening material of P. pumilus. With 

 regard to the development of the upper premolars of P. pmnilus, the 

 slightly more basined talon on P^ of the referred material is rather 

 general throughout and advanced over the condition noted in Protoreo- 

 don parvus, and particularly P. paradoxicus. P* shows perhaps less 

 conspicuous difference between P. pumilus and P. parvus, but in 

 P. paradoxicus the talon of P^ is much more bunodont. 



Protoreodon tardus is stated to be from the Beaver Divide con- 

 glomerate, in which case it is as late as, or later than, Protoreodon 

 primus, but the transverse width of the premolars is greater than is 

 regarded as characterizing that species, being more nearly as in P. 

 pumilus in this respect, as well as in size and degree of selenodonty ; 

 hence, it is tentatively included in the latter species. It may be further 

 noted that the division of the primary cusp and the development of 

 the talon or deuterocone portions of P^ and P* in the type of Pro- 

 toreodon tardus are perhaps a trifle less progressive than in most 

 referred material of P. pumilus, suggesting the smaller and even 

 earlier Protoreodon parvus. 



material of the three small artiodactyls (Eomeryx, Parameryx, and Oromeryx) 

 was found by himself in 1870. The labels, in Marsh's handwriting, accompany- 

 ing the material originally described as Agriochoeriis pumilus read "J. Heisey, 

 White River, Aug. 20th, 1874" and "S. Smith, Lake Fork, Aug. 9th, 1874." All 

 the Oromeryx and part of the Parameryx material has the field number 1057. 

 which was for the year 1877. The remaining material of Parameryx is labeled 

 "M. Forshay, Sept. 5, 1876." 



