NO. 20 RECOGNITION OF PLEISTOCENE FAUNAS HAY 3 



of glacial and interglacial stages, and they express the view that 

 during the interglacial times the glaciated regions were occupied 

 by numerous animals, among them many mammals. During the 

 glacial stages the animal and vegetable life was pushed southward, 

 and at each interglacial stage, it again migrated northward. The 

 authors likewise recognize the fact that there was a strong tropical 

 element in the fauna, made up partly of the great edentates and 

 peccaries. A northern element is believed to include the mammoths, 

 mastodon, bear, bison, reindeer, and musk-ox. Mingled with all, 

 in mid-latitudes, were forms on the verge of extinction, horses, 

 tapirs, llamas, and saber-tooth cats. 



In his Age of Mammals, 1910, Osborn adopts, in general, the 

 views of Cope, recognizing, however, four faunas, which he named 

 the fauna of the first or Equus-Mylodon zone; the fauna of the 

 second, or Megalonyx zone ; the fauna of the third, or Ovibos- 

 Rangifer zone ; and that of the fourth, or Cervus zone. The latter 

 fauna is that which existed at the time of the discovery of the con- 

 tinent by Columbus. The third fauna includes the musk-ox (Ovibos), 

 the reindeer, the mastodon, the hairy mammoth, and several species 

 of bison. The first and second faunas seem to be practically the 

 corresponding ones of Professor Cope. Professor Osborn holds 

 that the Equus-Mylodon fauna ocupied the dry Plains regions, but 

 also the coast of Florida (p. 452), while the Megalonyx fauna had 

 possession of the forested regions of the eastern part of the United 

 States and of the Pacific coast (p. 467). Professor Osborn, like 

 other students of the subject, recognized a South American con- 

 tingent in both of the earlier faunas. 



As to the time of the existence of the Equus-Mylodon and the 

 Megalonyx faunas, Osborn (p. 454) is inclined to believe that they 

 were to a great extent contemporary, but that probably early phases 

 of the Equus-Mylodon fauna antedated the beginning of the Mega- 

 lonyx fauna. 



In 1909 (Science, Vol. 30, p. 890) the present writer called at- 

 tention to the fact that no trustworthy discoveries of remains of 

 extinct horses had been made in deposits lying above the Wisconsin 

 drift, and he reached the conclusion that these animals had, in our 

 country, by that time, become extinct. 



Since that time the author has pursued the subject, and he 

 wishes here to present additional facts and conclusions. To aid in 

 this undertaking, he has prepared a base map of the mid-latitude 

 regions of North America, and represented on it the distribution of 



