LR Ay ae 
(c) for the articulation of the capitulum of a double- 
headed rib. The lower part of the same rim is bevelled 
in such a way (x) as to suggest that an invertebral 
wedge-bone may originally have been present. The 
neural canal produces a shallow groove in the centrum. 
The base of the neural arch (n. a.) still remains 
and proves that it is firmly fused with the centrum, 
not merely articulated by suture. This arch extends from 

Fig. I, Cervical vertebra. Vertebra cervical 
end to end of the centrum, but leaves a slight rim of 
the latter projecting in front. Its lateral portion is pro- 
duced somewhat downwards and ends in a deeply ovoid, 
rounded boss (t), for the articulation of the tuberculum 
of the rib already mentioned. It is thus evident that 
the rib must have been stout, deep, and antero-poste- 
riorly compressed at its double-headed upper end. 
One of the more imperfect vertebral centra is 
essentialy identical with that just described, showing 
