172 DINOCERATA. 



The Proboscidian line apparently went off from the main ungulate 

 stem in tlie Cretaceous. One branch ended in the later Pliocene in 

 Binotheritim ; another, in Mastodon ; while the genus Eleplias alone 

 survives, to represent this old group. 



Another strong branch, represented by a group which may be called 

 the HolodacUjla, probably also led off in the Cretaceous, and its typical 

 members, at least, had the following general characters : 



(1.) Brain, small and nearly smooth. 



(2.) Teeth, forty-four. 



(3.) Post glenoid process. 



(4.) Odontoid process, conical. 



(5.) Vertebra?, flat. 



(6.) Trunk vertebra?, twenty-three or more. 



(7.) Chevron bones. 



(8.) Pelvic bones, tirmly united. 



(9.) Femur with third trochanter. 



(10.) Ulna and fibula, complete. 



(11.) Fibula articulating with calcaneum. 



(12.) Five digits in manus and in pes. 



(13.) Carpal and tarsal bones more or less interlocking. 



(14.) Astragalus, nearly or quite flat. 



This line evidently divided near the base of the Eocene into the 

 great groups of Perissodactyls and Artiodactyls, each with many 

 off-shoots, and still existing. The former are now on the decline, and 

 have but three living rejjresentatives, the horse, the tapir, and the 

 rhinoceros. 



One off-set from the Perissodactyl line separated near the top of the 

 Eocene, where it is represented by Diplacodon, and perhaps ended in the 

 extinct Brontotherium, of the lower Miocene, although this line ma\' have 

 been continued somewhat later in the genus ChalicotheriuDi. 



From the Artiodactyl line, a peculiar group branched off in the early 

 Eocene, and in the Miocene was represented by Oreodon and allied genera, 

 and by later forms in the Pliocene. The Artiodactyls, now the dominant 

 ungulates, have numerous families, and many living genera and species. 



