13M) 
ile) 
or 
AXTAL SKELETON OF THE OSTRICH. 
THIRD VERTEBRA (natural size). 
Aspects. 
Fig. 15, dorsal; 16, ventral; 17, preaxial; 18, postaxial ; 19, lateral. 
Letters as before; and besides :—m, metapophysis; and ps, parapophysial 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, pc). 
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, pc). 
This surface differs 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. 
Stili its ventral margin is sometimes convex (not coinciding with the ventral margin of 
the central articular surface) ; but its dorsal 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). 
3k 2 
