364 THE VERTEBRATE SKELETON. 



Canine teeth are present in both jaws, and the grinding teeth 

 have short crowns, marked by V-shaped ridges. The pelvis is 

 large, the ilia are placed vertically, and the ischia do not take 

 part in the ventral symphysis. 



The best known animals belonging to this suborder are the 

 Uintatheriidae (Dinocerata) 1 , found in the Upper Eocene of 

 Wyoming. They are as large as elephants, and are charac- 

 terised by the long narrow skull drawn out into three pairs 

 of rounded protuberances, by the strong occipital crest, and 

 by the very large upper canines. 



Suborder (5). PROBOSCIDEA. 



This suborder includes the largest of land mammals, the 

 Elephants, and certain of their extinct allies. The limbs are 

 strong, and are vertically placed ; the proximal segment is the 

 longest, and the manus and pes are pentedactylate and sub- 

 plantigrade. The digits are all enclosed in a common integu- 

 ment, and each is provided with a broad hoof. The vertebral 

 centra are much flattened and compressed, especially in the cer- 

 vical region. The number of thoracic vertebrae is very great, 

 reaching twenty. The skull (figs. 96 and 97) is extremely large, 

 this being due to the great development of air cells, which 

 takes place in nearly all the bones of the adult skull. In the 

 young skull there are hardly any air cells, and the growth of 

 the cranial cavity does not by any means keep pace with the 

 growth of the skull in general. The supra-occipital is very 

 large, and forms a considerable part of the roof of the skull. 

 The nasals and jugals are short, and the premaxillae very 

 large. The rami of the mandible meet in a long symphysis, and 

 the ascending portion is very high. Canine teeth are absent, 

 and the incisors have the form of ever-growing tusks composed 

 mainly of dentine; in living forms they are present in the 

 upper jaw only. The grinding teeth are large, and in living 



1 See 0. C. Marsh, "The Dinocerata," U. S. Geol. Survey, 1884, 

 vol. x. 



