PHYLOGENY OF THE PALAZOGNATHA AND NEOGNATHA, 205 
pterygoid above and the palatine below. A portion of this flange-like plate of the 
palatine helps to fill up the cleft between the pterygoid fork already described. As 
mentioned above, the palatine rests upon a backwardly directed plate from the maxillo- 
palatine process, the whole of which it conceals from the dorsal aspect. Ventrally, 
this process is found to run along, and below, the external palatine border, and to 
terminate near its extreme posterior end. ‘The forward extension of the palatine on 
the ventral surface corresponds with the level of the tip of the vomer. ‘This extension 
is derived from the ventral surface-layers of the main body, the palatine terminating 
abruptly on the dorsal aspect ina V-shaped notch at the level of the middle of the 
vomer. ‘[his ventral process rests in a groove along the mesial border of the maxillo- 
palatine process. 
The relations of the vomer have already been more or less indicated. Suffice it to 
say, that the free end of each posterior limb is wedged in between the spine-like 
extremity of the pteryguid above and the flange-like inward projection from the dorsal 
surface of the palatine below. 
The palate of Apteryx will be found, ona close comparison with that of the remaining 
Paleognathe, to have departed from the typical Struthious form in the direction of 
that taken by Rhea, the relations between palatine and vomer being similar in both. 
The form of the pterygoid differs from that of all other birds, in that it is bifid, or, in 
that it sends off a separate limb whose mesial border passes downwards to underlie the 
external border of the palatine. ‘This external, palatine limb is elsewhere unrepre- 
sented. ‘The internal, vomerine limb may be regarded as a flattened plate folded upon 
itself, the edge being inwards. ‘The superior edge, or upper lip, must be regarded as 
representing the mesial border of an originally flattened pterygoid such as that of 
Dromeus. 
The dentary is of great length. In Dromeus, Casuarius, Rhea, Apteryx, and 
‘Tinamous it extends backwards to within one-fourth of the whole length of the ramus. 
It is relatively less in Struthio. Caudad each ramus divides into dorsal and ventral 
limbs, of which the ventral is the larger. In Rhea the dorsal limb is paired. 
The splenial is of great length in all, extending forwards to the symphysis of the 
jaw, and backwards to within a short distance of the level of the glenoid cavity for the 
quadrate. It is rod-like in Struthio, laterally compressed in the remaining forms. 
The angular, in all save Apterya, articulates, proximally, with the supra-angular, 
being embedded caudad in its external border; distally, it twists downwards so as to 
form the ventral border of the ramus. In Casuarius and Dromeus its extreme posterior 
and inner border comes into contact with the articular. In Rhea and Struthio, it falls 
considerably short of this. 
In Apterya, the angular articulates proximally with the ventral border of the 
articular, which is hollowed out to receive it. ‘The supra-angular rests upon its 
dorsal border. 
VoL. XV.—Pak?T v. No. 13.—December, 1900. 26 
