52 PROF. G. B. HOWES AND MR. H. H. SWINNERTON ON THE 
region to have been the first seat in order of time of the development of dermal 
plates }. 
Passing to the palate, it is seen that at this stage approximation is most marked in 
front, for while the vomers have met in the middle line, the pterygoids are widely 
divaricated behind. A noticeable feature is the fact that the palatines, which support 
the orbital floor, have apparently shared in the afore-mentioned rapidity of growth. 
From this stage onwards, the salient feature in progressive development is the closing 
in towards the middle line of the bones of both the cranial roof and palate, rendered 
possible by the fact that the most rapid phases in the growth of the brain have now 
passed. Comparison of Pl. III. figs. 11 & 12, and Pl. IV. figs. 5, 6, and 8, will 
render clear the changes undergone in the individual bones during the process, which 
it is not necessary to describe in words. 
It is at the stage (R) that the parasphenoid first appears, in the form (PI. III. 
fig. 12, p.s.; im section in Pl. IV. fig. 1) of a minute bony element which would most 
certainly be lost to sight in ordinary dissection, lying freely beneath the antero-median 
border of the post-pituitary plate. With advancing development it assumes an arrow- 
head shape and a more intimate relationship with the basis cranii, fusing by its broad 
posterior extremity at Stage S with the basisphenoids, and closing the pituitary foramen 
as it does so by extension anteriorly (Pl. IV. fig. 3). 
We have already drawn attention (anted, p. 2) to the interest attaching to this bone. 
It was overlooked by Ginther, Brihl, and others, and its discovery was first claimed 
by Fritsch, who believed he had observed it as an independent element?. Baur 
immediately challenged the alleged independence *, and gave an accurate account of 
its limitations in a young individual. Fritsch compared the supposed parasphenoid 
with that of Hyloplesion, and comparison of his figure of this with that given by 
Credner (op. cit. p. 513) of the presumed co-ossified basi- and preesphenoids of 
Paleohatteria at once arouses suspicion by the close similarity in shape of the two; 
while further complication arises from the fact that Baur, commenting on Credner’s 
discovery, regards* his basi-presphenoid as a parasphenoid alone. Fritsch for 
Sphenodon, and Credner for Paleohatteria, were dealing with the compound basi- and 
parasphenoid, and were therefore in error. Baur was right only in his delimitation 
of the parasphenoid of Sphenodon. 
The pterygoids, as already remarked, are developed widely apart, apposition in the 
middle line commencing anteriorly at Stage R, at which (Pl. III. fig. 12, pg.) they 
already reach the vomers—/. é., their forward extension is thus recognizable as soon as 
* Cf. Newberry, J. S.: Monogr. U.S. Geol. Survey, vol. xvi. 1889, p. 103, pl. xliv.; and Jeckel, O.: Sitzb. 
Ges. naturf. Fr. 1892, p. 90, 
* Fritsch, A.; Fauna d. Gaskéhle d. Permform. d. Bohmen, Bd. ii. 1889, p. 58. 
Baur, G.: Zoolog. Anzeiger, Bd. xii. 1889, p. 45. 
* Baur, G.: Amer. Journ. Sci. 1889, p. 311, 
