326 Prof. D. M. S. Watson on 



Ptery(ioi(L — The structure oE tlie pterj'goid has long been 

 well known. It is a triangular bone, veiy deep posteriorly, 

 where it extends down to the quadrate and up to the nieta- 

 pterygoid. Between these two bones its outer surface bears 

 a deep groove, bounded anteriorly by a strong rounded ridge. 

 In front of this ridge the upper border is nearly straight, lies 

 paralhd to tbe upper edge of the parasphenoid, and must 

 liave been very powerfully attached to that bone by a tough 

 membrane during life, because specimens are not uncommon 

 in which the whole skull, except the sphenoid, parasphenoid, 

 and pterygoids, has been lost. In a specimen of this sort 

 in my collection both metapterygoids were removed before 

 burial wathout any displacement of the pterygoids. 



Anteriorly the lower edge of the pterygoid turns outward, 

 so that the oral surface of the bone becomes inclined at only 

 a small angle to the horizontal. 



The lateral margin of the pterygoid anteriorly is grooved 

 for the reception of the ectopterygoid. 



Palatine. — The palatine is a small quadricylindrical bone 

 wliose iiinder end is underlain by the pterygoid. The inner 

 part of the bone stands vertically and lies against the w^all of 

 the anterior end of the parasphenoid. 



The anterior end of the bone is pointed and lies in a groove 

 on the lateral and under surface of the bone called by Stensio 

 a pre-ethmoid. 



The palatine has no teeth attaclied to it, and might, if 

 viewed in the light of teleost morphology, be regarded as an 

 autopalatine — that is, an ossification in the palato-quadrate 

 cartilage. The texture of the bone and the details of its 

 sntiu-e witli the pterygoid differ, how^ever, from those of the 

 nietapterygoid, and there is really no sound reason for re- 

 garding it as other than a strict homologue of the Tetrapod 

 palatine. 



Loosely attached to the oral surface of the palatine is 

 a thin bony plate, consisting mainly of the fused bases of a 

 multitude of minute teeth; this element bears a single large 

 tusk, which lies in an area, also including a shallow concavity 

 for the development of its alternative tooth, surrounded by a 

 circle of denticles somewhat larger tlian those which cover 

 most of the bone. This element might be considered a 

 dermo-palatine if the palatine be called auto-palatine ; but, 

 although probably homologous to that element in Teleosts, I 

 prefer to regard it merely as a product of the fusion of teeth. 

 Vomer (?). — The element which for the moment I regard as 

 a prevomer is tliat which is described by Stensio as a pre- 



