278 



CAPT. D. M. S. WATSON ON SEYMOURIA, 



The odontokl is a single bone. Its upper surface is slightly 

 rounded but presents no trace of any articulation. The posterior 

 surface is not exposed. The anterior surface is slightly convex, 

 rising to a small point. This surface is in general triangular 

 with the point at the mid-ventral surface. The lateral edges are 

 slightly emarginate at about the middle of their height so as to 

 divide the whole area into three ; of these, the lowest articulates 

 with the anterior intercentrum, and the two dorsal with the 

 neural arches. The lateral surface is nearly fiat, but rises some- 

 wha.t towards the ends ; it is triangular, so that there must be a 

 gap for a triangular intercentrum between the odontoid and the 

 axial centrum. 



Text-figure 8. 



f\. 



D. 



D. 



F i--.-M!l:\! 



Setjmonria haijloriensis Broili. X 2.- 



A. Odontoid from in front-. 



B. Atlantal intercentrum from in front. 



C. Atlantal intercentrum from below, anterior end upward. 



D. Third intercentrum and centrum from below. 



E. Fourth centrum and fifth intercentrum. 



Axis. — The second vertebra preserved difiers in no important 

 respect from the third and fourth. It has large well-formed and 

 somewhat swollen zygapophyses, which are not very much pro- 

 duced laterally, the lateral part of the neuiul arch immediately 

 below the articular surface beini>- extended outward into a shoit 



