514 THE VERTEBRATE SKELETON. 



In the SIRENIA the pelvis is quite vestigial. In the Dugong 

 it consists on each side of two slender bones, one of which 

 represents the ilium and the other the ischium and pubis ; the 

 two bones are placed end to end and are commonly fused 

 together. The ilium is attached by ligament to the transverse 

 process of one of the vertebrae. In the Manatee each half 

 of the pelvis is represented by a triangular bone connected by 

 ligaments with its fellow and with the vertebral column. In 

 neither Manatee nor Dugong is there any trace of an aceta- 

 bulum but one can be made out in Halitherium. 



In the CETACBA the pelvis is even more vestigial than in 

 the Sirenia, consisting simply of a pair of small straight bones 

 which probably represent the ischia, and lie parallel to and 

 below the vertebral column at the point where the develop- 

 ment of chevron bones commences. 



In UNGULATA VERA the pelvis is generally rather long and 

 narrow. The ilium is flattened and expanded in front (fig. 

 103, 8), but becomes much narrower and more cylindrical 

 before reaching the acetabulum. Both pubis and ischium 

 contribute to the symphysis which is often very long. The 

 ischia are large and have prominent tuberosities, especially in 

 Artiodactyles. In most Ruminantia there is a deep depression, 

 the supra-acetabular fossa above the acetabulum, but this is 

 not found in the Suina or Tylopoda. 



SUBUNGULATA. In Procavia the pelvis is long and narrow, 

 and bears resemblance to that in Artiodactyles. 



The Proboscidea have a very large pelvis set nearly at 

 right angles to the vertebral column ; the ilium is very wide, 

 having expanded iliac 1 and gluteaP surfaces, and a narrow 

 sacral 1 surface. The pubes and ischia are rather small, but 

 both meet their fellows in the symphysis. Uintatherium (sub- 

 order Amblypoda) also has a large and vertically placed pelvis 

 (fig. 108) with a much expanded ilium. The pelvis however 



1 See p. 409. 



