ART. 1. PRIMATES OF THE FORT UNION GIDLEY. 17 



distinctively primate, is, however, not observed in all groups of the 

 order. But the stage just described, which in the Notharctidae is 

 followed by the budding off of a hypocone from the posterior flank 

 of the protocone, seems to have been an important basis of modifi- 

 cation in all the anthropoids, including man, and in some but not 

 all groups of Lemurs. The molar pattern of modern anthropoids 

 seems to have been built on this model. 



The general molar structure just described is most clearly distin- 

 guished in some of the South American monkeys, but is somewhat 

 obscured in most of the Old World forms through the greater develop- 

 ment of the hypocene and the general evening up of the four prin- 

 cipal cusps in all the molars to form a subequally quadricusped tooth. 

 Even in these, however, the double basin, or valley structure still 

 persists although greatly modified by the lowering and enlargement 

 of the four main cusps of the molar crown, and the consequent shift- 

 ing of the anterior and posterior basins to the same level. 



It would thus seem that the similarity of the molars of Noihodectes 

 to those of the Notharctidae after all has more significance than was 

 conceded by Matthew, and, taken together with the character of the 

 premolars and of the incisors as above interpreted, leaves little doubt 

 regarding the primate affinities of the Plesiadapidae. 



Since writing the above. Doctor Matthew has informed me in con- 

 versation that the American Museum now has additional material of 

 Nothodedes which includes associated foot bones. These, according 

 to Matthew, are " tupaioid-insectivore in type." For this reason he 

 now concludes that the Plesiadapidae are not Primates but should be 

 considered true insectivores. I can not, however, entirely concur 

 with Matthew in this opinion, for, granting the tupaioid character of 

 the foot bones of Nothodectes, this would mean nothing beyond indi- 

 cating a primitive condition which might be expected in almost any 

 of the earlier groups of Primates, especially in view of the fact that 

 the living Tupaiids are primatelike in many important features. 



In interpreting the meaning of a tupaialike foot structure in these 

 early forms, the fact must be considered that the Twpaia foot more 

 nearly resembles that of the little-specialized South American Pri- 

 mates than it does other living families of insectivores. Comparison 

 of the hind foot of Hapale with that of Twpaia shows such striking 

 resemblances that were the bones of these two types of feet found 

 fossil in the same beds they would be difficultly separable, and would 

 surely be considered not more than generically distinct. It would 

 seem, therefore, that the tupaioid-insectivore, or Menotyphla, type 

 of foot may have given rise to the primate types. If, therefore, a 

 living primate has retained a foot structure which, if not typically 

 tupaioid, is directly derivable from such a type, might it not natu- 

 5596— 24— Proc.N.M.voI.63 2 



