458 H. F. Osborn — Mammalia in North America. 



Hyracotherium in the ancestry of the horses. Similarly the 

 Microbiotheriidse are the stem of the creodonts and carnivores. 

 I cannot coincide with any of these views. The Multituber- 

 culates are far older and widely different from the Abderites 

 to which Ameghino traces their ancestry. I fully concur with 

 the opinion of Cope, Zittel, Scott and others that this fauna is 

 of somewhat later age, that it was directly connected with Aus- 

 tralia and somewhat later with North America, supplying us, 

 as has always been supposed, with our sloths. I quote from a 

 recent address by Scott : 



" The oldest mammals from South America are those from 

 Patagonia, which Ameghino has referred to the Eocene, but 

 which are more probably Oligocene or Miocene. This fauna 

 is of extreme peculiarity and isolation ; it is made up chiefly 

 of edentates, rodents and ungulates of those very aberrant types 

 known as Litopterna and Toxodontia, which are so widely dif- 

 ferent from the hoofed mammals of the northern hemisphere ; 

 together with some primitive forms of primates, creodonts and 

 marsupials. The marsupials are of extraordinary interest, for 

 they comprise not only forms allied to the opossums, but also 

 to recent Australian forms such as Thylacinus, Dasyurus and 

 Hypsiprymnus. This is a most unexpected fact and seems to 

 point unmistakably to a great southern circumpoiar continent." 



The North American Puerco thus remains the most exten- 

 sively known and productive lower Eocene center yet we have 

 very slender threads of positive evidence to connect its fauna 

 with the later placental radiation. 



The Creodonts of Cope occupy the same relation to the 

 modern insectivores and carnivores that the Condylarthra do 

 to the ungulates. The American group has been recently en- 

 riched by the discoveries of Wortman, and the literature by 

 the careful revision of Scott. This author has divided them 

 into eight families, placing the forms which most resemble the 

 Insectivora in the new family, Oxyclsenidge. These families 

 illustrate superbly the same law of functional radiation later 

 repeated in the placental and marsupial carnivores. The 

 Mesonyx family presents some analogies to the Thylacines. 

 The modern bears are paralleled in the Arctocyons, with their 

 low tubercular molars ; Wortman and myself, with fresh materi- 

 als, have recently added Anacodon to this family, a genus which 

 was doubtfully regarded by Cope as an ancient ungulate. The 

 Cats and Hysenas are imitated in the Oxysenas and Hyseno- 

 dons, some of the Miocene forms of which Scott suggests 

 developed aquatic habits ; as above noted, some of this family 

 acquired large brains and persisted well into the Miocene. A 



