CHAPTER X. 



THE PELVIC ARCFI AND TAIL. 

 (Plates XLI, XLII, XLIII, LV, and LVI.) 



The Pelvis. 

 (Plates XLI-XLII; and woodcuts l.'U-l.-'.f), lielow.) 



In all the known specimens of tlie DiiKicemtd in wliicli the ])elvic 

 arch is preserved, tlie iliiuii, ischium, and puln's are firndy cdiisiHed with 

 each other, but not with the sacrum. The three pelvic bones on each 

 side nnite with eacli othc^r earlier, and much more closely, than they do 

 with the sacrum above, or with the opposite pelvic boiuss below. The 

 sutures for the latter union remained open until the animal Avas fully adult, 

 and, even then in some specimens, were readily separated. These 

 features are well shown in Plate XLI. 



Tlie pelvis of Dinoceras may be compared Avith that of the ele|)haut, 

 to which it bears a considerable resemblance, but from which it ditifers in 

 many important particulars. 



The ilia are nnich expanded, and nearly quaclrant-sha|ied in outline, 

 the supra-iliac border being very regularly curved, ami only moderately 

 thickened near its union with the acetabular border, wliich it joins at about 

 a right angle. The iliac surface is moderately concave in liotli directions, 

 especially near the surface for union with the sacrum. 



The gluteal surface is nearly flat where most ex])anded, but becomes 

 convex in the acetabular region. It rises but little above the sacral 

 articular surface, winch is short, somewhat triangular in outline, and 



