644 MANUAL OF ZOOLOGY. 



don davipes, from the tip of the snout to the end of the tail, 

 was more than nine feet. 



All these gigantic South American Edentates occur in Post- 

 tertiary deposits. Older, however, than any of these is the 

 Macrotherium. This is a gigantic Edentate, intermediate in 

 some respects between the Pangolins and Orycteropus, and 

 found in certain lacustrine deposits of France, of Miocene 

 age. 



Order IV. Sirmia. This order contains only the living 

 Manatees and Dugongs, and is of little geological importance. 

 The Halitkcrium, however, of the Eocene, Miocene, and Plio- 

 cene rocks, is a large form, intermediate between the African 

 Manatee and the Dugong. 



Order V. Cetacea. The Cetacea, also, are of little geological 

 importance. Remains of Rorquals have been found in the 

 Pliocene, and some of the ear-bones of the Crag (Pliocene) are 

 probably referable to true Whalebone Whales. The Physe- 

 teridce commence in the Pliocene, the Delphinidce. in the 

 Miocene, and the Ziphioid Whales in the Pliocene. The 

 Ztuglodontida, like the other Cetaceans, are only known from 

 the Tertiary Rocks, but Zeuglodon commences in the Eocene. 



Order VI. Ungtilata. The hoofed Mammals are repre- 

 sented in past time by so many extinct forms that it will be 

 wholly impossible here to do more than merely allude to some 

 of the more important genera. 



The earliest-known Ungulates occur in the Eocene rocks, 

 where the order is represented by very numerous and interest- 

 ing forms, the more important of which are Pliolophus, Palceo- 

 therium, and Anoplotherium. 



Of the section of the Ungulates comprising the living Horse, 

 Zebra, and Ass (Solidungula), the earliest fossil example is the 

 Anchitherium of the Lower Miocene, and this was succeeded 

 by the Hipparion of the Miocene rocks. This genus differed 

 from the existing Equida in the presence of two small toes 

 with hoofs, one on each side of the single functional toe, 

 which alone remains in living horses ; whilst in Anchitherium 

 the lateral toes were sufficiently developed to touch the ground. 

 In the Pliocene period appear, for the first time, remains of 

 , horses which, like the present form, possessed only a single toe 

 encased in a single hoof. It is interesting to observe that one 

 of the Pliocene horses (Equus curvidens) occurs in South 

 America ; though this continent certainly possessed no native 

 horse at the time of its discovery by the Spaniards. About 

 twenty horses one of them standing no more than two and a 

 half feet in height have been described from North America, 



