.^., STUDY OF MAMMALS DURING 1891. 105 



Marsupials, Creodonts, and true Carnivores are closely related. We 

 may add that the asserted occurrence by MM. Moreno and Mercerat 

 of a large Monotreme in the Patagonian Tertiaries will, if confirmed, 

 strongly support the connection of the South American Tertiary fauna 

 with the existing fauna of Australia, 



Another very important event of the year is the discovery of 

 numerous remains of small monkeys in the Lower Tertiary — 

 ? Eocene — of Patagonia, which have been described by Professor 

 Ameghino^ as Homnncnlus, AntJiropops, Hoinocentriis, and Eudiasfatus. 

 The mandibles of these (Figs. 4 and 5) show the three premolar 

 teeth characteristic of the American monkeys, and apparently belong 

 to the family Cebidae ; they are remarkable for the extreme upright- 

 ness of the chin. If the Patagonian strata be rightly correlated with 

 the European Eocene, we have now evidence of the existence of 

 Anthropoid Primates at a much earlier date than has hitherto been 



Fig. 6.— Skeleton of the rijiht hind foot of Icochilus robiistiis — natural size. 



recorded. Perhaps still more noteworthy are the signs of affinit}' 

 exhibited by these early Primates to the extinct South American 

 Protypotheriida^. The latter are clearly related to the aberrant 

 Ungulate Typothennm of the South American Tertiaries, which 

 appears to be allied on the one hand to the extinct Toxodon, and on 

 the other to the Rodents, Protypotheviuni and the allied Icochilus 

 differ, however, by having all their teeth in contact, and by the 

 terminal phalanges of the digits being expanded for flattened nails 

 (Fig. 6) while both the thumb and great toe were opposable to the 

 other digits. If substantiated, such an unexpected relationship as 

 that of the American Primates to the Toxodonts will materially 

 modify some of our present views as to the mutual relationships of 

 mammals. We are indebted to Professor Ameghino for the figures 

 of the remains of these monkeys and Icochilus. 



■' Rcvist. Argent. Hist. Nat., vol. i., pp. 383-397, 1S91. 



