NO. 7 MAMMALIA FROM THE ALMY FORMATION GAZIN I5 



MEASUREMENTS OF UPPER TEETH IN SPECIMENS OF 



Phenacodus alniiensis 



Length of cheek tooth series, P*-M*, inclusive 



Length of molar series, M^-M", inclusive 



P^ anteroposterior diameter : transverse diameter . . 

 P*, anteroposterior diameter : transverse diameter.. 

 M\ anteroposterior diameter : transverse diameter * 

 M^ anteroposterior diameter : transverse diameter * 

 M^ anteroposterior diameter : transverse diameter * 



• Approximate. 



* Anteroposterior diameter of upper molars taken perpendicular to anterior margin and 

 transverse diameter across anterior portion. 



PHENACODUS PRIMAEVUS Cope, 1873 

 Plate 2, figure 5 



Tvi^o specimens in the collection may well represent typical Phena- 

 codus primaevus. One of these, U.S.N.M. No. 21287, is a lower jaw 

 with P3 to M2, inclusive, and the other an incomplete lower molar. 

 The teeth in No. 21287 ^-^e comparable in size to those in the Qark 

 Fork material referred to P. primaevus. The length of the lower 

 molars is near the lower limit of the range given for each (Simpson, 

 1937b, p. 18) and the widths are nearer the upper limit, suggesting 

 relatively broad teeth, not otherwise distinguished from P. primaevus. 



About eight specimens of smaller size, though not comparable to 

 P. almiensis, correspond in general proportions to Gray Bull materials 

 earlier regarded as Phenacodus intermedins. The dimensions of teeth 

 in one of these (U.S.N.M. No, 20644), evidently the largest of the 

 group, are given in the accompanying table. In this and others having 

 comparable lower molars the teeth are observed to be relatively slen- 

 der, particularly in comparison with the larger, broad-toothed form 

 discussed above. A single specimen encountered by Simpson (1937b, 

 p. 19) in the Clark Fork collections, representing a smaller group 

 which approximates the intermediate-sized form in the Almy fauna, 

 was regarded by him as Phenacodus primaevus, small var., cf. inter- 

 viedius. The Almy materials may be treated in a similar manner, for 

 taxonomic convenience, because, although the limited Almy materials 

 might appear to be clearly defined, I find it difficult to distinguish 

 P. intermedins from P. primaevus in the Gray Bull collections. Never- 

 theless, I feel rather strongly opposed to a concept which recognizes 

 more than one subspecies of the same form coexisting in time and at 

 the same geographic locality. 



