336 NATUEAL SCIENCE [May 



approximately parallel in their development on both continents, 

 only differing in some minor branches whicli soon became extinct. 

 The camels, however, are clearly American throughout, only 

 wandering into the Old World by Asia in the Pliocene. It is 

 almost equally probable that the oxen originated in the Old World. 



Among Carnivora, the Creodonta are both American and 

 European ; but on the former continent they only pass upwards 

 into the dogs (Canidae), weasels (Mustelidae), and the aberrant cats 

 of the family Nimravidae, while in Europe they are succeeded not 

 merely by these families, but also by the Viverridae, Hyaenidae, 

 Felidae, and Ursidae. The viverroids and hyaenas never reached 

 America, but the true cats and bears arrived in that continent at 

 the close of the Pliocene. 



Of the Primates, the primitive lemuroids appeared in the 

 Eocene similarly on both continents ; but in North America they 

 soon became extinct, while in the Old World they were followed 

 by the true apes, and still have some specialised survivors. 



A. Smith Woodward. 



