676 THE POPULAR SCIENCE MONTHLY. 



such perfect preservation as to suggest a very recent period for their 

 extinction. The Sloth tribe is represented by the huge Mylodon, 

 Megatherium, Megalonyx, Ccelodon, Ochotherium, Gnathopis, Zesto- 

 don, Scelidotherkim, and Sphcenodon ; and among the Armadilloes 

 were Chlamydotherium, Eurydon, Glyptodon, ETeterodon, Pachythe- 

 rium, and Schistopleurum. Glossotherium, another extinct genus, is 

 supposed to be allied to the Ant-Eaters. 



It is frequently asserted, and very generally believed, that the 

 large number of huge Edentata which lived in North America during 

 the Post-Pliocene were the results of an extensive migration from 

 South America soon after the elevation of the Isthmus of Panama, 

 near the close of the Tertiary. No conclusive proof of such migration 

 has been offered, and the evidence, it seems to me. so far as we now 

 have it, is directly opposed to this view. No undoubted Tertiary 

 Edentates have yet been discovered in South America, while we have 

 at least two species in our Miocene, and, during the deposition of our 

 lower Pliocene, large individuals of this group were not uncommon 

 as far north as the forty-third parallel of latitude, on both sides of the 

 Rocky Mountains. In view of these facts, and others which I shall 

 lay before you, it seems more natural to conclude, from our present 

 knowledge, that the migration, which no doubt took place, was from 

 north to south. The Edentates, finding thus in South America a con- 

 genial home, flourished greatly for a time, and, although the larger 

 forms are now all extinct, diminutive representatives of the group still 

 inhabit the same region. 



The Cetacea 1 first appear in the Eocene, as in Europe, and are 

 comparatively abundant in deposits of this age on the Atlantic coast. 

 The most interesting remains of this order, yet found, belong to the 

 Zeuglodontidce, which are carnivorous whales, and the only animals 

 of the order with teeth implanted by two roots. The principal genera 

 of this family are Zeuglodon and Squalodon, the former genus being 

 represented by gigantic forms, some of which were seventy feet in 

 length. The genus Saurocetes, which includes some small animals of 

 this group, has been found in South America. The Dolphin family 

 {Delphinidce) are well represented in the Miocene, both on the Atlan- 

 tic and Pacific coast. The best-known genus is Priscodelphinus, of 

 which several species have been described. Several other generic 

 names which have been applied to fragments need not here be enu- 

 merated. In none of the Tertiary species of this family were the 

 cervical vertebra? anchylosed. The Sperm Whales ( Catodontidm) 

 were also abundant throughout the Tertiary, and with them, in the 

 earlier beds, various Ziphioid forms have been found. The toothless 

 Balmnidaz are only known with certainty as fossils from the later 

 Tertiary and^ more recent deposits. 



1 Cctarca, an order of marine mammals which includes among its living representa- 

 tives the whales, dolphins, porpoises, narwhal, etc. 



