DEVELOPMENT OF THE SKELETON OF THE TUATARA. 45 
With advancing development, the chondrifying centre of the quadrate cartilage 
extends into the pterygoid and epipterygoid processes in common, and with this 
replacement there comes about the afore-mentioned rotation, under which the epi- 
pterygoid process, originally directed backwards and downwards, comes to be upwardly 
directed, the pterygoid bar being displaced accordingly. On the assumption of this 
rotation and its definitive position, the quadrate portion elongates and develops two 
processes—a dorsal or otic process (fig. 4, g.'), and a lower process, which appears 
correlatively with the segmentation off of Meckel’s cartilage. Anteriorly its pterygoid 
portion turns suddenly outwards and expands (cf. espec. Pl. III. fig. 6, pg.'). Con- 
tinuing to elongate, it comes at Stage R to overlie the pterygoid and the inner half 
of the os transversum, tapering to a point. Gaupp describes this cartilage in the 
Lacertilian as merely extending ‘in the direction of ” the transversum. He points 
out (Berichte, p. 9) that did it continue forwards it would enter the maxillary region 
and that of the processus maxillarius posterior (our fourth extranasal process) of the 
nasal capsule, it would realize the condition occurring in Ranodon and the Anura. 
With this we fully agree; but we regard the extension over the transversum as 
indicative of the retention by Sphenodon of a more approximately batrachian condition 
than that thus far known for the Lacertilia. 
In Sphenodon the study of the nerves and all possible relationships leaves no doubt 
that the epipterygoid process is the homologue of the processus ascendens of the 
batrachian quadrate cartilage, as recognized by Gaupp. He, however, seems to us 
somewhat in doubt’ as to the actual occurrence in the Lacertilian embryo of a 
cartilaginous connection between the epipterygoid “ Anlage” and the quadrate. 
In Sphenodon, so far from there being any doubt on this matter, not only are the 
epipterygoid and quadrate originally preformed in one continuous cartilaginous tract, 
but, from Stage R onwards, the portion of this which, after the establishment of these 
two bones, remains, begins to ossify by extension of the quadrate centre, to form the 
characteristic antero-dorsal quadrate lobe (Pl. IV. fig. 11), the presence of which 
accounts for the close relationship of the epipterygoid and the quadrate in the adult. 
The difference with the reduction of the jugal arch and the liberation and freedom of 
the quadrate associated in the Lacertilia is one in respect to which the gap between 
these and the Rhynchocephalia is immensely greater than between them and the 
Chelonia 2, to say nothing of the Crocodilia and other reptiles possessed of a fixed 
‘ Gaupp, E., especially in his paper in Anat. Anz. Bd. vi. 1891, p. 107, and Berichte cit. 1898, pp. 9-11. 
2 We can only express astonishment, mixed with regret, at the gratuitous assumption by Osawa (98 °% 
p- 102), in seeking to explain away the Giintherian dictum concerning the relationships of the quadrate to 
the pterygoid, that the latter arises from two ossific centres, of which the hinder has in Sphenodon become 
co-ossified with the quadrate. There is no trace of any such posterior pterygoid bone actual or potential. 
