MATTHEW, CLIMATE AND EVOLUTION 197 



Pleistocene. Hippidion and Onohippidion are found (fide Koth) in 

 somewhat older levels ; but as they are much advanced over anything in 

 our Middle Pliocene (Blanco), it would seem that their first occurrence 

 in the Pampean must be placed at the top of the Pliocene or preferably 

 in the lower Pleistocene. I conclude that the Pampean formation ap- 

 proximately represents the Pleistocene epoch. 



Beneath the Pampean of Ameghino, but included in it by Roth, are 

 fossiliferous beds in which certain Procyonidse and Ursidfe are found. 

 If we admit the North American source of these carnivora, they would 

 indicate Pliocene age for the beds containing them. Dr. Ameghino, who 

 regards them as Oligocene and Miocene, is compelled, therefore, to set 

 aside the North American ancestors of the Procyonida? and to regard 

 them as of South American origin and the Ursidse as either autoch- 

 thonous or arriving in South America from the Old World via Africa. 

 As with the Equidte, the only shadow of plausibility for such phylogenies 

 lies in the incompleteness and careful limitation of the evidence that is 

 adduced in their behalf. Phlaocyon of the North American Miocene, 

 which is intermediate between Cynodictis and the Procyonidae in almost 

 every detail of the perfectly preserved dentition, skull and skeleton is 

 merely-* "un vrai Canide sans relations avec les Procyonides," while the 

 South American genera are derived through hypothetical ancestors from 

 the carnivorous marsupials of the Santa Cruz. Here again, Dr. Ameghino 

 is compelled, in defense of his theories of correlation, to adopt these im- 

 possible phylogenies, because if the Procyonids are of North American 

 origin the Argentine formations are demonstrably of later date than 

 those which he assigns to them. Phlaocyon is a far more primitive 

 procyonid than any of the South American genera. Leptarctus of the 

 Upper Miocene may be their equivalent, but it is very imperfectly 

 known. -^ If these Argentine genera are derived from the Oligocene 

 Cynodictis and related genera of Holarctica, Phlaocyon being about half 

 way between the two groups, then their age is indicated as Pliocene, not 

 as Oligocene or Miocene. Also with the Ursidre ; to admit them as arriv- 



al Pl. Ameghino : Ann. Mus. Nac. Buenos Aires, torn, xv, p. 396. 1906. Dr. von Ihering 

 has since attempted to prove wliat Ameghino merely asserted. His argument rests upon 

 an untenable interpretation of a single feature in the dentition, ignoring all other char- 

 acters of teeth, skull and skeleton, and, if true, would involve not only that Bassarisciis 

 has nothing to do with the Procyonidae (which he asserts), but also that the ProcyonidiB 

 have nothing to do with the carnivora but are of wholly diverse ancestry. 



See H. V. Ihering, Systematik, Verbreitung und Geschichte der sudamerikanlschen 

 Raiibthlere. Archiv f. Naturg., 76 .Tahrg. I. Bd., s. 113-179. 1910. 



^ The type of Leptarctus is an upper premolar of doubtful affinities. Wortman re- 

 ferred to it in 1894 a lower jaw from the Upper Miocene, which is unquestionably 

 procyonid and hardly distinguishable from Procyon. Ameghino and von Ihering ignore 

 this record. 



