92 



MAEINE EEPTILES OF THE OXFOED CLAY. 



of which nothing can be seen in Murcemsaurus. Williston's * figure of the mandible 

 of Cimoliosawus snowii seems to show that in that species the structure was very 

 similar to that above described. 



Vertebral Column. — The vertebral column consists of 43-44 cervicals, 2 or 3 pectorals, 

 20 dorsals, 3-4 sacrals, and an unknown number of caudals. The cervical series forms 

 the greater part of the column, and in the type specimen oi Murcenosaurus leedsi the 

 neck was about 210 cm. long. 



The atlas and axis (text-fig. 49) are always closely united in adult specimens, but in 

 young individuals the lines of division between the different elements are quite distinct. 



Text-fig. 49. 



axa 



n.c 



'OOCC 



a.wlh 



Atlas and axis of Murcenosaurus durohriveiisis : A, from right side ; B, from front. (E. 2863, nat. size.) 

 ai.a., neural arcli of atlas ; a.w.h., anteinor Avedge-bone ; ax.a., neural arch of axis ; ax.c, centrum of axis ; 

 7iy.»-., hypapophjrsial ridge; n.c, neural canal; oc?., odontoid ; ?p.w'.&., ? posterior wedge-bone ; /".^ rib 

 of atlas ; r.^, rib of axis. 



The atlantal cup for the occipital condyle is deeply concave, and its diameter from 

 above downwards is a little longer than from side to side. By far the greater part of 

 it is formed by the anterior end of the odontoid [od.) process, which is here as large as 

 or larger than the centrum of the axis. Its antero-ventral angle is cut away and unites 

 with the anterior wedge-bone [a.w.h.), the front of which completes the lower portion 

 of the atlantal cup. Above, the odontoid unites with the bases of lateral pieces of the 

 neural arch of the atlas (ctt.a.). The union with these is not very extensive, since they do 



Ojp. cit. (1903) p. 52, fig. 13, and pi. v. fig. 5. 



