AXIAL SKELETON OF THE OSTKICH. 



403 



The postaxial articular surface of the centrum has the transverse extent of its ventral 

 margin very little in excess of that of its dorsal margin. The articular surfaces of the 

 prezygapoplnjses look more directly dorsad and less inwardly ; those of the posfziffia- 

 pophyses are broader. 



The median unexcavated part of the neural spine is again more or less longer antero- 

 posteriorly. The postaxial part of the neural arch still more nearly approaches in 

 width the preaxial part of that arch than in the tenth vertebra ; and its postaxial 

 margin is less concave. 



The Twelfth Veetebea. 



The twelfth vertebra carries on the progressive modifications indicated in tlie 

 eleventh vertebra, and it is slightly longer and more massive than that vertebra. 



The catapophyses may here first project ventrally as sharply marked processes 



(figs. 30 & 32, c). 



TWELPTH VEETEBEA (f natural size). 

 Fig. 29. Fig. 30. 



Fig. 31. 



Aspects. 



Fig. 29, lateral ; 30, postaxial ; 31, dorsal ; and 32, ventral. 



Letters as before ; c, catapophysis. 



The transverse extent of the postaxial part of the neural arch nearly equals that of 

 its preaxial part. 



The styliform rib here generally attains its maximum of length. 



3l2 



