344 MR. W. P. PYCRAFT ON THE MORPHOLOGY 
their relation one to another, and to the maxillo-palatine process, 
in the accompanying figures. 
In the palate of Rhea (Pl. 31. fig. 2) the vomer is relatively 
smaller than in Dromeus. It is deeply cleft anteriorly, thereby 
exposing the parasphenoidal rostrum, which is concealed in 
Dromeus when the skull is viewed ventrally, and posteriorly 
it terminates in a pair of broad “feet” closely approximated. 
Furthermore, the vomer is peculiar in that it is trough-shaped, 
the parasphenoid being received into the trough. The feet of 
the vomer, if further examined from the ventral aspect of the 
skull, will be found to be partly concealed by the palatines. 
Thus the primitive position of the palatines, which obtains in 
Dromeus, has in Rhea undergone a change. They have moved, 
from their original position outside the vomero-pterygoid bar, 
towards the middle line, and in doing so have come to underlie 
this bar. 
This movement of the palatines inwards, and their connection 
with the distal end of the pterygoid, has played a very important 
part in the evolution of the avian palate. 
We may trace the early stages in this movement of the 
palatines in the skull of the Tinamous. 
The palate of the Tinamous, as I have already pointed out, 
closely resembles that of Rhea. This close resemblance being 
undeniable, we need only concern ourselves here with the 
differences between the two skulls. The most important of 
these differences for the present connection are concerned with 
the vomer, palatine, and pterygoid. 
The pterygoid, in the Tinamous, appears to be relatively 
longer than in Rhea. This appearance is deceptive, and is really 
due to the fact that the vomer and palatines have shifted 
considerably forwards, whereby the vomer terminates much 
further forward along the parasphenoidal rostrum—so much so, 
that the choane (which are narrower than in hea) le almost 
entirely in front of, imstead of almost entirely behind the ant- 
orbital plate (prefrontal), terminating immediately beneath the 
bony style (lachrymo-nasal pillar), taking the place of the 
maxillary process of the nasal. In other words, the choanze 
extend forwards as far as the anterior limit of the lachrymo- 
nasal fossa. 
The palatines of the Tinamous have become more rod-shaped. 
