of the Skull in Peloneustes philarchus. 249 
one half is on the transpalatine, the other on the pterygoid * ; 
it then passes backwards, and reaches the hinder border 
of the palate about 8-eentim. from the middle line (see 
woodcut 3). 
The posterior border of the lateral ramus is thickened and 
passes by a curve into the lateral border of the posterior wing, 
the two forming the anterior and internal lower borders of the 
temporal fossa. ‘The lateral border of the posterior ramus is 
somewhat concave, and its edge is thick and rounded; poste- 
riorly it passed outward and backwards, forming the front 
border of the long posterior prolongation of the bone which 
unites suturally with the inner edge of the quadrate imme- 
diately above the condyle for the mandible; this posterior 
process extends considerably behind the occipital surface. 
In the middle line for about 10 centim. behind the vomers 
the pterygoids unite with one another; behind this point they 
are separated by a median bone, which is here regarded as a 
parasphenoid. Viewed from the dorsal surface it can be seen 
that this bone extends nearly to the vomers, but ventrally it 
is overlapped by the pterygoids as far back as the point 
mentioned. About opposite the hinder border of the lateral 
ramus, at a spot about 11 centim. in advance of the tinder- 
most point of the occipital condyle, the median borders of 
pterygoids become thickened and rounded, and, curving out- 
wards, diverge from the parasphenoid. Further back they 
again approach the median line, and finally unite with one 
another in a median suture about 3 centim.(?) long, over- 
lapping the basisphenoid and anterior portion of the basi- 
occipital, the former of which is completely covered by them. 
The two foramina thus enclosed between the pterygoids and 
the basis cranw are about 6 centim. long by 1 to 2 wide; 
they were described by Owen in an impertect skull referred 
by him to Plestosaurus rostratus. He, however, considered 
that the pterygoids, and not the basis cranii, formed the 
median bar, and that these bones met the palatines opposite 
the anterior end of these foramina, which he calls the 
“‘palato-nares,” apparently supposing that the nasal passages 
were prolonged backward to this level by the union of the 
palatines and pterygoids, somewhat as in the Crocodilia. The 
true internal nares, as was shown in the foregoing descrip- 
tion, and as Huxley suspected, lie very much farther forward, 
and these posterior openings, which may be spoken of as 
the posterior palatine vacuities, have nothing to do with the 
* This downwardly-projecting process of the palate is homologous with 
an exactly similarly constituted process in Sphenodon, many Lacertilia, 
the Crocodiles, and, apparently, the Theriodontia. 
