CAVES AND THEIR CONTENTS 153 



genus. Megalonyx and Mylodon, which follows in Pliocene 

 times, were giant ground sloths almost the size of elephants, 

 while Glyptotherium, another Pliocene species, had a great 

 shield -like bony armour covering the whole body. The plio 

 cene species were accompanied by a great peccary (Platy- 

 gonus), a llama of a very large size (Pliauchenia) and a 

 number of other interesting creatures, all of which have now 

 completely vanished from the northern continent. 



In the succeeding deposits from the great plains and moun- 

 tain regions, which have been classified by Professor 

 Osborn * as belonging to the lower Pleistocene series, we 

 notice the remains of two large elephants (Elephas columbi 

 and E. imperator), a true camel (Camelus) and two other mem- 

 bers of the same family, the great peccary Platygonus and the 

 two large ground sloths, Mylodon and Paramylodon. The 

 rivers were tenanted by beavers, otters, musk rats and a 

 curious semi -aquatic creature about the size of a bear, called 

 Castoroides. Belated to some of the groups of South American 

 rodents, the latter suddenly makes its appearance in the 

 Pleistocene beds of eastern North America. 



Now we come to the cave deposits, which I have alluded to 

 already on several occasions, and which Professor Osborn 

 includes in the middle Pleistocene or Glacial series. The 

 Port Kennedy cave in Pennsylvania contains no less than 

 four species of the great edentate Megalonyx, also a Mylodon, 

 two kinds of sabre -tooth tigers, a Mastodon, four species of 

 peccaries and a tapir. In the Potter Creek cave of California 

 were discovered, among others, four species of Megalonyx, a 

 camel and a Mastodon. Finally, the Conard fissure of 

 northern Arkansas revealed two species of sabre-tooth tigers, 

 three kinds of peccaries and numerous small animals. Apart 

 from a few deer bones and the remains of the curious Symbos^ 

 an animal allied to the musk ox, it contained no traces of large 

 ungulates. Their presence in the district adjoining the fissure 

 is, nevertheless, indicated by the sabre -tooth tigers. 



What I wish to make clear is that huge creatures requiring 

 an abundance of vegetable food poured into North America, 

 not only in Pliocene but also in Pleistocene times. Many 



* Osborn, H. F., " Cenozoic Mammal Horizons," p. 85. 



