VERTEBRATE LIFE IN AMERICA. 675 



Returning now to our subject from this geological digression 

 which will hardly be deemed unprofitable, since I have given you in 

 few words the results of a great deal of my own hard mountain work 

 let us consider the Tertiary mammals, as we know them front the 

 remains already discovered, and attempt to trace the history of 

 each order down to the present time. We have seen that a sin- 

 gle small Marsupial, from the Trias, is the only mammal found in 

 all the American rocks below the Eocene ; and yet in beds of this 

 age, immediately over the Chalk, fossil mammals of many different 

 kinds abound. 



The Marsupials, strange to say, are here few in number, and di- 

 minutive in size ; and have as yet been identified only by fragmentary 

 specimens, and most of them are too imperfect for accurate descrip- 

 tion. In the higher Eocene deposits, this group is more abundant, 

 but still represented by small animals, most of them insectivorous, or 

 carnivorous in habit, like the existing opossum. From the Miocene 

 and Pliocene, no remains of Marsupials have been described. From 

 the Post-Tertiary, only specimens nearly allied to those now living 

 are known, and most of these were found in the caves of South 

 America. 



The Edentate 1 Mammals are evidently an American type, and on 

 this continent attained a great development in numbers and size. No 

 Eocene Edentates have been found here, and, although their discovery 

 in this formation has been announced, the identification proves to have 

 been erroneous. In the Miocene of the Pacific coast, a few fossils 

 have been discovered which belong to animals of this group, and to 

 the genus Moropus. There are two species, one about as large as a 

 tapir, and the other nearly twice that size. This genus is the type 

 of a distinct family, the Moropodidoz. In the lower Pliocene above, 

 well-preserved remains of Edentates of very large size have been 

 found at several widely-separated localities in Idaho and California. 

 These belong to the genus Morotherium, of which two species are 

 known. East of the Rocky Mountains, in the lower Pliocene of Ne- 

 braska, a large species apparently of the genus Moropus has been dis- 

 covered. The horizon of these later fossils corresponds nearly with 

 beds in Europe that have been called Miocene. In the Post-Pliocene 

 of North America, gigantic Edentates were very numerous and widely 

 distributed, but all disappeared with the close of that period. These 

 forms were essentially huge sloths, and the more important genera 

 were Megatherium^ Mylodon, and Megalonyx. The genera Mega- 

 looms and Myomorphus have been found only in Cuba. 



In South America, during the Pliocene or Post-Pliocene, enormous 

 Edentates were still more abundant, and their remains are usually in 



1 The Edentates are an order of Mammals, in which the teeth are imperfect or want- 

 ing. The teeth when present are without enamel, or true roots. This order includes the 

 sloths, armadilloes, ant-eaters, etc. 



