AXIAL SKELETON OF THE OSTEICH. 



395 



THIED VEETEBEA (natural size). 

 Pig. 15. Fio;. 16. 



Fig. 19. 



Aspects. 



Fig. 15, dorsal; 16, ventral; 17, preaxial ; 18, postasial ; 19, lateral. 



Letters as before ; and besides : — m, metapophysis ; and ps, parapopbysial root of pleurapophysial lamella. 



much, nor in the same way, as the postaxial surface of the centrum of the axis differs 

 from that vertebra's preaxial surface (fig. 18, ^jc). 



The postaxial surface of the body of the third vertebra closely resembles the corre- 

 sponding surface of the axis, while it presents a corresponding but inverted relation to 

 its own preaxial central surface, being strongly convex transversely and concave dorso- 

 ventrally, the whole surface looking dorsad as well as postaxiad (figs. 15 & 19, ^c). 



This surface difiers from the corresponding surface of the axis in that its ventral part 

 is not prolonged ventrad into a hypapophysial process, in that its extreme dorso-ventral 

 diameter is less in proportion to its extreme transverse dimension, and in that the trans- 

 verse extent of the dorsal margin exceeds that of the ventral margin to a less degree. 

 Still its ventral margin is sometimes convex (not coinciding with the ventral margin of 

 the central articular surface) ; but its dor.sal and lateral margins seem always concave. 



The neural surface of the centrum, but for its greater length, is very like that of the 

 axis, abstraction being made of the (here absent) odontoid process. 



The preaxial margin of the neural surface is strongly concave ; its postaxial margin is 

 slightly convex (fig. 15). 



3k2 



