100 



the inner and narrower end of the section is convex. The first lower 

 molar in the Scelidothere corresponds in form with the first upper molar, 

 and is consequently easily distinguishable from the corresponding tooth 

 in the genus Mylodon. 



489. The cervical vertebra?. 



The cervical vertebrae present the ordinary mammalian number, seven, 

 and are free or so articulated as to permit of reciprocal movement upon 

 each other. Their transverse processes are perforated as usual for the 

 vertebral arteries. These processes in the atlas are remarkable for 

 their great breadth, length and thickness ; and indicate that the mus- 

 cular force which must have worked the head upon the spine was 

 very powerful. The axis is provided with a robust " processus dentatus," 

 having a base equal in breadth to the body of the axis itself, and a 

 smooth articular convexity on the side of the apex on which the ring of 

 the atlas rotated. The line of union between the axis and its characteristic 

 process, which here resembles the body of an abortive vertebra, is very 

 distinct. The transverse processes of the vertebra dentata are compara- 

 tively feeble, but this condition is amply compensated for by the great 

 development of the spinous process. This process is bent backwards 

 at nearly a right angle, overlaps with its reflected extremity the spine 

 of the third cervical vertebra, and rests by its base, on the under part 

 of which are the posterior articular surfaces, upon the broad and strong 

 anterior oblique processes of the third vertebra. The third, fourth, 

 fifth and sixth cervical vertebrae have moderately developed and pointed 

 spinous processes ; their transverse processes are broad, and extend 

 obliquely backwards and slightly overlap each other. On the under 

 part of the transverse process of the sixth cervical vertebra there is the 

 fractured base of what I conjecture to have been an expanded aliform 

 plate, analogous to that observable in the corresponding vertebra of the 

 Orycterope. The seventh cervical vertebra has part of the articular de- 

 pression for the head of the first rib upon each side of its body : the 

 transverse process is feebly developed, but the spine is double the height 

 and size of those of the preceding vertebrae. 



