27 



mentary specimens, and most of them too imperfect for accurate 

 description. In the higher Eocene deposits, this group is more 

 abundant, hut still represented by small animals, most of them 

 insectivorous, or carnivorous in habit, like the existing Opos- 

 sum. 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 Mammals are evidently an American type, 

 and on this Continent attained a great dcvelojmicnt 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 Mio- 

 cene 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 dis- 

 tinct family, the Mompodidce. 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 Morothernim, of which 

 two species are known. East of the Rocky Mountains, in the 

 lower Pliocene of Nebraska, a large species apparently of the 

 genus Aloropus has been discovered. 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 im})ortant genera 

 were Megatherium^ Mylodon and Megalonyx. The genera 

 Mefjalocnns and Myomorpltus 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 such perfect preservation as to suggest 

 a very recent period for their extinction. The Sloth tribe 

 is represented liy the huge Mylodon^ Megatherium^ Megahnyx, 



