THE GEOLOGICAL RECORD. 103 



supials, once widely distributed, remain only in Aus- 

 tralia, where they have escaped from competition with 

 the more advanced Placentalia, and as scattered genera 

 in America. The Dugong and Manatee are now the 

 only representatives of the order Sirenia ; while the 

 Edentata, including the gigantic ground Sloths (Mega- 

 therium) and Glyptodonts, once all-powerful in South 

 America, are reduced nowadays to a few highly-special- 

 ised tree-sloths and armadillos (Fig. 6). 



Most instructive is the history of the large order 

 Ungulata, which includes all the hoofed herbivorous 

 mammals. Starting in Eocene times from primitive 

 forms about the size of a fox> with complete unspecialised 

 dentition and five-toed feet, known as the Condylarthra, 

 and long ago extinct, the Ungulates branched out into 

 a number of sub-orders (Fig. 7). The Amblypoda de- 

 veloped into huge creatures, like Dinoceras, with large 

 tusks and four horns on the skull, but did not survive 

 beyond the Eocene age. A somewhat similar but quite 

 distinct group of massively-built herbivores, the Titano- 

 theria, lasted only into the Miocene, while the highly- 

 specialised and aberrant sub-order Ancylopoda occurs 

 up to the Pliocene epoch. Two South American groups, 

 the formidable rhinoceros-like Toxodontia and the more 

 horse-like Litopterna, have left no descendants. The 

 Hyracoidea survive at the present day only in the little 

 coney, Hyrax, and a closely-allied genus ; and of the 

 Proboscidea, including mastodons, mammoths, and 

 elephants, a large group once widely distributed over 

 both the Old and the New World, there persists but one 

 species in Asia and one in Africa. Even the large sub- 

 order Perissodactyla (the odd -toed Ungulates), although 

 still represented by a few rhinoceroses, tapirs, horses, 

 and asses, is by no means as widespread or successful as 

 it once was. The even-toed Artiodactyla are at present 

 the most nourishing group, with a large number of genera 

 and species of deer, antelopes, sheep, rind oxen. But 



