No. 2.] THE RELATIONS OF PROTOCERAS. 335 



Protoceras. Moschus. 



Third lumbar, length of centrum 0.024 m. 0.024 m. 



Fourth lumbar, length of centrum 024 .024 



Fifth lumbar, length of centrum 019 .024 



Third lumbar, width of transverse process at base . . . .017 .011 



Third lumbar, fore and aft diameter of spine on .021 



First caudal, length of centrum 015 .012 



First caudal, breadth of anterior face 014 .005 



First caudal, breadth of posterior face 013 .004 



V. The Fore Limb. 



The Scapula (PI. XXI, Fig. 10) is entirely ruminant in 

 character and quite different from that of the primitive artio- 

 dactyls. In outline it forms a high, narrow triangle, with very 

 slender neck. The glenoid cavity is shallow and nearly circu- 

 lar in shape and the coracoid forms a prominent, recurved hook, 

 which is entirely like that of Moschus. The spine is placed 

 near to the anterior margin, so that the prescapular fossa is 

 very much smaller than the postscapular. The spine itself 

 rises rapidly from the suprascapular border and becomes un- 

 usually high and prominent ; its free border is not, as in most 

 ruminants, an erect edge, but almost from the start is curved 

 over toward the posterior side, the curvature increasing distally. 

 Thus, the hinder surface of the spine is deeply concave and its 

 front convex in a manner resembling the scapular spine of 

 Mesoreodoti, but unlike that genus, there is no distinct meta- 

 cromion. The acromion is longer, broader and thicker than in 

 the existing Pecora. The coracoid border is not quite straight, 

 but rises from the neck with a slight curvature, which is con- 

 cave below and convex above. The other two borders are 

 straight. Both the coracoid and glenoid borders, and especially 

 the latter, are thickened and elevated, making both the pre- 

 and postscapular fossae somewhat concave. The subscapular 

 fossa is also rendered slightly concave by the elevation of its 

 borders. 



The Hwneviis is short and stout. The head is large, strongly 

 convex in the antero-posterior direction and projecting back 

 much beyond the line of the shaft ; it is much larger in pro- 

 portion to the length of the bone than in MoscJms. The ex- 

 ternal tuberosity is very large, forming a high, massive ridge. 



