182 PROF. W. K. PARKER ON THE STRUCTURE AND 
Under the orbital region the parasphenoid scarcely lessens its width ; but in front, 
opposite the ethmo-palatine (¢. pa), it narrows into a rounded but splintery end, which is 
covered by the vomers (v). 
These latter bones (v) look larger than they are; for they are ankylosed to the 
palatines (pa); together these bones reach along two fifths of the inner edge of the 
maxillaries. 
The vomero-palatine bones are separated from the marginal series by a curved fossa, 
which is nearly a quadrant; and their fore edge is covered with a second row of 
rasp-like teeth; but these are smaller than the outer row. 
The two vomers are united by a harmony suture, and end behind as broad, splintery 
flaps, the right flap being the larger of the two. Behind the teeth they are roundly 
notched as if for the inner nostrils (7. 7); but these are much further outwards, and a 
tract of the membranous nasal floor intervenes. 
The palatines (pa) are so much of the compound bones as lie outside these notches ; in 
front they bulge into the crescentic valley, and thus reveal their existence as additions 
to the vomer; they end as an ear-shaped lobe to each large bony tract. 
The pterygoids (pg) which arose as edentulous outgrowths of the palatines, are 
separated from them by a space larger than the latter bones; they are thickish, 
smooth, angular slabs of bone, whose main part is obliquely four-sided or lozenge- 
shaped, and from which there grow two large angular processes that look forwards, 
and one that grows far backwards. The inner process, in front, runs forwards, 
binding the parasphenoid and sphenethmoid, and ending where they end. The outer 
front process is not far from the jugal process of the maxillary, and carries the remnant 
of the pterygoid cartilage (¢.pg). The hind process carries the inner arcuate edge of 
the bone backwards to the hinder margin of the quadrate condyle (g.c); this long, 
retral process clamps the quadrate bone inside as strongly as the squamosal does above. 
The space between the two front processes has a gnawed edge, and the upper surface 
(fig. 1) is scooped, within for the optic nerve (11), and without for the pterygoid cartilage 
(¢-p9). 
Also along its upper part, postero-laterally, the pterygoid forms a solid scooped 
floor for the unossified proximal parts of the suspensorium (a. p, ot. p). 
The mandibles together form three fourths of a very regular oval; and the dentaries 
(Pl. XXXIX. fig. 4, d) form a large part of each ramus; they reach yery nearly to the 
angle behind. Their upper or dentigerous edge (Pl. XX XVIII. fig. 3, d, spl) is thick, 
and their infero-lateral surface is rounded; they meet at the chin by a broad surface. 
The splenidals (sp/) are also dentigerous ; they are slenderer by far than the dentaries, 
do not reach so far forward, but go further backward, where they dilate and form a 
coronoid crest ; for indeed they answer to both splenial and coronoid. 
The articulars (a) are properly ectosteal plates, and set up ossification in the 
cartilage; they are strongly wedged in between the other two bones. 
