150 PROCEEDINGS OF THE ACADEMY OF [Jail.^ 



If speculation be fui'ther indulged in as regards the manner in which 

 the descendants of cretaceous or eocene lemurs could be transformed 

 into Platyrrhine monkeys like those living at the present day, it is 

 readily seen, as suggested by Leidy,® ''that but little change would be 

 necessary to evolve from the jaw and teeth of Nothardus that of a 

 modern monkey. The same condition which would lead to the sup- 

 pression of a first premolar in continuance would reduce the fangs of 

 the other premolars to a single one. This change with a concomitant 

 shortening and increase of depth of the jaw, would give the character 

 of a living Cebus. A further reduction of a single premolar would give 

 rise to the condition of the jaw in the Old World apes and man." In 

 the imion of the rami of the jaw at the symphysis, in the small size of 

 the condyle, in the number of the incisors, canines and true molars, 

 nearly alike in their constitution and in their crowded condition, the 

 lower jaw of Nothardus resembles most strikingly that of a Platyi'rhine 

 monkey. Like Leidy, both Cope and Marsh regarded the Platyrrhine 

 monkeys, on the one hand as the descendants of extinct lemurs, and, 

 on the other, as the ancestors of the Catarrhinse. 



Thus Cope,^ basing his \dew upon the structure of Tomitherium, 

 offered as a possible phylum the following: 



Homo 



I 

 Sitniidae 



1 

 Cebus 



I 

 Hapale 



I 

 Lemur 



Tomitherium 



though later, as we shall see presently, he modified the above view^ 

 somewhat, finally regarding man and the anthropoids as having 

 probably descended directly from extinct lemurs hke Anaptomorphus. 

 By similar reasoning from the study of closely affiliated, if not identical, 

 Lemuroid genera: Limnotherium (Tomitherium), Antiacodon (Anapto- 

 morphus), Marsh,® in referring to the origin of the Primates, was 

 led to the conclusion that "we may justly claim America for the birth- 

 place of the order." 

 Why the Old World apes, when difterentiated, did not come to the 



s Extinct Vertebrate Fauna, 1873, p. 90, 



' Mammalia Educabilia, Am. Phil. Soc, 1873. 



.*' Lemuroidea, etc., American Naturalist, 1885, p. 467. 



^ Vertebrate Life in America, 1877, p. 52. 



