MAMMALIA. 71 



throughout the world during the Eocene period. Zeuglodon 

 (yoke-tooth), thus named by Owen in allusion to the shape 

 of its hinder teeth (Fig. 67b), has jaws so peculiar that they 

 were originally supposed to belong to a reptile, which was 

 termed Basilosaurus. The skull (Fig. 67a) is not completely 

 that of a whale, though it is elongated and depressed, with 

 the nostril on the middle of the upper surface. Each side of 

 either jaw is provided with four simple teeth in front and 

 five double-rooted teeth behind. The neck must have been 

 unusually long for a whale and not rigid. There are also 

 traces of an armour of small bony plates. Plaster casts of 

 the skull and teeth, besides actual teeth of the typical 

 Zeuglodon cetoides, from the Eocene of Alabama, U.S.A., are 

 exhibited, proving the animal to have been of rather large 

 size. A plaster cast of part of a skull of Z. osiris from Egypt 

 is also shown. 



Order IX.— EDENTATA. 



The sloths, anteaters, and armadillos have been cha- 

 racteristic of the South American region since early Tertiary 

 times, and they do not appear to have wandered farther than 

 the southern part of North America at any period. They are 

 quite a degenerate and insignificant race at the present day, 

 compared with their former representatives. 



The modern sloths and anteaters are almost unknown Wall-ease 

 among fossils, but the peculiarities of both these families are TaMe-case 

 combined in the skeleton of the extinct ground-sloths. 14b, 15a. 

 These animals, in fact, exhibit the head and teeth of a sloth CaBe Y - 

 associated with the back-bone, limbs, and tail of an anteater. 

 They lived in great numbers in South America during the 

 latter part of the Tertiary period, ranging even so far north 

 as Kentucky in the Pleistocene ; and some of them survived 

 to be contemporaries of man at a very recent Prehistoric 

 date. The Miocene or perhaps Upper Eocene forms are quite 

 small, but they become larger as they are traced upwards 

 in the geological sequence, and many of the Pleistocene 

 and Prehistoric species rival elephants and rhinoceroses in 

 bulk. 



The best known ground-sloths are Megatherium, Scelido- 

 iherium, and Mylodon, all well represented in the collection. 

 They obviously could not live in trees like the little sloths 

 which exist at present in the South American forests ; but 

 their hind quarters are very massive and their stout tail 

 would serve with their hind legs to form a rigid tripod on 



