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ANNALS NEW YORK ACADEMY OF SCIENCES 
cene; it is unknown from the Old World; Felis is doubtfully identified in the 
Middle Pliocene (Blanco), certainly present in the Pleistocene of North 
America. 
From these data it appears to the reviewer that the northern elements of 
the Middle and Upper Pampean fauna were derived, certainly in large part, 
probably entirely, from North America, by a migration not earlier than the 
beginning of the Pleistocene. The Lower Pampean may however be con¬ 
siderably older; its few northern genera — Pararctotherium, Pachynasua, 
Cyonasua, Microtragulus etc., are aberrant or imperfectly known forms of 
more archaic aspect, approximately derivable from the Miocene carnivora 
etc. of North America, but decidedly more specialized. 
CHARACTERISTIC GENERA OF THE SOUTH AMERICAN CENOZOIC 
WITH PROVISIONAL ORDINAL REFERENCES (W. D. M. 1 )- 
I. Notostylops Fauna. 
Marsupialia (Polyprotodontia). 
Caroloameghinia (with bunodont molars). 
Marsupialia (Diprotodontia, ? Multituberculata). 
Propoly mastodon. 
Polydolops, Orthodolops, Pliodolops. 
Edentata (Dasypoid genera only). 
Meteutatus etc. 
Condylarthra (including genera allied to Periptychidse). 
Didolodus (cf. Ectoconus, but with quadrate molars). 
Ricardolydekkeria, Gulielmofloveria (cf. Anisonchinse). 
Asmithwoodioardia, Notoprotogonia (cf. Euprotogonia). 
Proectocion (cf. Ectocion and Phenacodus; also cf. Litopterna). 
Nephacodus, Lonchoconus (cf. Phenacodus). 
? Henricosbornia. 
Litopterna (primitive brachyodont genera of) 
Lambdaconus (astragalus certainly Litoptern). 
? Archaeohyracotherium, ? Oldfieldthomasia (cf. also Toxodontia). 
Toxodontia (inch Typotheria, primitive genera of) 
Notopithecus. 
Insectivora. 
? ? Selenoconus is stated by Ameghino to be closely allied to Hyopsodus, 
which is a very generalized animal of remote insectivore relationships. 
It is known only from part of the lower jaw. 
1 The geological occurrence of the genera is based chiefly upon Ameghino’s published lists 
(1908). The reviewer is responsible for their systematic reference. 
