THE SKELETON 31 



anterior rim of the internal narial opening and a part of the orbit. 

 It carries a very characteristic S-shaped dentigerous ridge which 

 extends far backwards in the mouth and turns lateralwards under the 

 ear capsule. This posterior extension is quite free from the overlying 

 part of the skull (parasphenoid), and is separated from it by soft 

 tissues, including the M. retractor bulbi, which passes dorsal to the 

 posterior end. The pattern of this dentition is of taxonomic im- 

 portance (cf. p. i). 



As already suggested, the older workers, e.g. Parker and 

 Wiedersheim, regarded it as representing both the vomer and the 

 palatine elements fused together, and named it accordingly vomero- 

 palatine. In 1 9 10 Wintrebert, as the result of an investigation of the 

 metamorphosing skull, came to the conclusion that the palatine en- 

 tirely aborts during the change from larval to adult life, and that the 

 bone under consideration should therefore be regarded as the vomer. 

 In 1924 Stadtmiiller, whose careful and detailed work on the de- 

 velopment of the skull has already been mentioned, declares that in 

 all his examples the vomer appears to fuse with the palatine, but 

 that it is extremely difficult to decide whether this is really the case, 

 or whether the latter is entirely resorbed, as Wintrebert claims. He 

 criticizes Wintrebert's work on account of the absence of any 

 figures, details of methods, and size of the larvae investigated, 

 and says that he prefers to agree with the older investigators. 

 He nevertheless confirms Wintrebert's statement that the vomerine 

 part has a double origin, while he does not discuss the possibility of 

 an homology with the pre-vomer. He had not seen Wintrebert's 

 chief paper (1922) against which his criticism certainly could not 

 be levelled. 



The whole question therefore remains sub judice and its solution 

 lies outside the scope of the present work, but in view of the 

 evidence of palaeontology the newer terminology has been adopted 

 here. 



The pterygoids (o.pt.) are a pair of more or less ploughshare-shaped 

 bones investing the pterygoid cartilages of the primary cranium, 

 the cartilages lying in a groove on the dorsal surface of each investing 

 bone. The posterior end of the bone lies under the quadrate, and 

 extends laterally almost to the jaw articulation and mesially over the 

 processus basalis. The anterior extremity points antero-laterally to- 

 wards the posterior extremity of the maxilla but does not quite meet 

 it, and hence the bone forms the posterior margin of the orbit. 



Kesteven identifies this bone with the reptilian ectopterygoid or os 

 transversum rather than with the reptilian and mammalian pterygoid, 



