248 



ME. C. W. ANDBEWS ON THE STETTCTT7EE [May 1896* 



shown in this specimen. It rises from the upper surface of the 

 pterygoids about opposite their junction with the basisphenoid ; 

 its base of attachment is very long from before backward, so that 

 it extends for a considerable distance along the upper edge of the 

 quadrate process of the pterygoid. In its middle portion it con- 

 tracts in width, and is an elongate oval in section. On both sides 

 of the skull the upper portion of this bone has unfortunately been 

 broken away, so that the junction with the parietals is not clear, 

 but it evidently joined their lower edge at about their middle point. 

 The palatines (pal.) are elongated plates of bone, of which the 

 anterior edges form the hinder margin of the nares ; on the inner 

 side they unite in front with 



Fig. 1. — Palatal surface of the Skull 

 of Plesiosaurus dolichodeirus. 



(About ^ natural size.) 



the vomers, and behind with 

 the pterygoids, while on the 

 outer they join the maxilla?. 

 In the present specimen the 

 relations of the hinder border 

 of the palatine are not clear, 

 though it is evident that in- 

 ternally it joined the lateral 

 ramus of the pterygoids; 

 but in a skull of P. dolicho- 

 deirus (B.M. Coll. 41101) 

 it can be seen (fig. 1) that 

 externally the hinder border 

 of the palatine joined the 

 transpalatine for a short 

 distance, and was then 

 separated from it by a 

 small suborbital foramen 

 (sub-orb. vac.) which appears 

 to be closed on its outer 

 side by the maxilla. Mr. 

 Lydekker l first called atten- 

 tion to these foramina in this 

 specimen (fig. 1), in which 

 also he first observed the fact 

 that the pterygoids extend 

 forward to meet the vomers. 

 The vomers (vom.) are 

 not well preserved ; they 

 are long narrow bones which 

 unite, and perhaps anchylose, 



in the middle line. Posteriorly they join the pterygoids, and in 

 front of these, the palatines. About the middle of their length 

 they form the division between the internal nares, and anterior 

 to these apertures they run forward between the maxilla? and pre- 

 maxilla?. 



Cat. Toss. Rept. Brit. Mus. pt. ii. (1889) p. 257, no. 41101. 



