1904.] NATURAL SCIENCES OF PHILADELPHIA. 151 



land of their earlier ancestry is readily explained by the then inter- 

 vening oceans, which likewise were a barrier to the return of the horse 

 and rhinoceros. Man, however, came doubtless first across Behring's 

 Straits, and at his advent became part of our fauna as a mammal and 

 primate. 



As a confirmation of the view that the Platyrrhinse have descended 

 from monkeys, it may be mentioned that while the remains of Cebus, 

 Mycetes, Callethrix, and Hapale have been found, according to Ame- 

 ghino,^" in the Pleistocene strata of Brazil, extinct lennn-s, such as 

 Notopithecidffi and Homunculidge, have been discovered recently, 

 according to the same high authority, in the eocene deposits of South 

 America." Indeed, according to Ameghino," the Homunculidce are 

 to be regarded as the ''ancetres de tous les singes du nouveau que de 

 I'ancien continent les lemurs excepte." Cope appears to have taken 

 the same view as that expressed by Ameghino. In speaking of certain 

 extinct forms of monkeys found in Patagonia, he remarks that they 

 ''appear to be ancestors of the existing South American monkeys 

 (Cebidffi), and possibly of the Old Yvorld m.onkeys also."^^ 



It should be mentioned, however, that these fossils are regarded 

 by some paleontologists as being rather the remains of Platyrrhine 

 monkeys than lemurs. Should such prove hereafter to be the case, it 

 will not weaken the argument, since in that case the forms in question^ 

 if not lemurs, would be intermediate in character between the latter 

 and Platyrrhine monkeys. The remains of Catarrhine monkeys, such 

 as Papeo, Macacus, Semnopithecus, and possibly even of the chimpan- 

 zee and orang, have been found in the Pliocene deposits of India." 



Such facts are, however, not inconsistent — indeed, have little or no 

 bearing upon the question of the derivation of Catarrhine from Platyr- 

 rhine monkej^s — since the only assumption that would be necessary 

 would be to suppose that the Platyrrhine ancestors of the fossil Plio- 

 cene Catarrhines existed once in India or elsewhere. It may be said, 

 however, that this is assuming the very question at issue, a case of 

 petitio principii; but the reverse proposition, that the Platyrrhine 

 have descended from the Catarrhine monkeys, is untenable, being incon- 

 sistent with the w^ell-established fact that the more ancient members of 

 a group of animals had always more teeth than the later more recent 



1" Adas Sciencia.'i Cordoba, T. VI, 1S89, p. 101. 

 " Bol. Acad. Nac. Buenos Aires, T. XVII, 1902, p. 7. 

 12 Op. cif., T. XIII, 1902, p. 265. 

 " Organic Evolution, 1896, p. 154. 



1* Flower and Lyddeker, Mammals Living and Extinct, 1891, pp. 723, 727 

 738. 



