562 F. B. Loomis — New Mosasaur from the Ft. Pierre. 



with concave faces on the rear and anterior sides. The axis 

 lias a stout nodular hypophysis below and heavy transverse 

 processes. The posterior articular end of the centrum is con- 

 cave and almost circular in outline. The remaining cervicals 

 are similar in shape, except that the centrum is convex in front 

 and concave behind and the hypophyses are progressively 

 smaller. Each carried a small rib on its transverse process. 



The dorsal vertebrae have no hypophyses. The transverse 

 processes are short and heavy, and from the anterior of each 

 process a heavy ridge extends forward continuing into the pre- 

 zygapophysis. The spines are of moderate height and each 



Fig. 4. 



Fig. 5. 



Fig. 4. 

 Fig. 5. 



A dorsal vertebra (6) 1/4 nat. size. 

 A caudal vertebra (8) 1/4 nat. size. 



about as broad (antero-posteriorly) as the length of the cen- 

 trum. The postzygapophyses are small and situated above the 

 neural canal on the spines. Each pair is close together, mak- 

 ing the interlocking of the vertebrae very close. The neural 

 canal is remarkably small. 



The pygal vertebrae* (noncostiferous) number five, have no 

 hypapophyses, very large transverse processes, weak zygapo- 

 p'hyses and strong spinous processes. 



On the caudals the transverse processes at the anterior end 

 grow progressively smaller toward the rear and soon disappear. 

 On the ventral side are chevrons which are free and articu- 

 lated with the lower surfaces of the centra. In the anterior 



