56 rXSH 6ALLEEY. 



with the exception of the first (atlas) and last, are provided with 

 ribSj many of which are bifid (73). A series of flat spines (73), 

 called interneurals, to which the spines and rays of the dorsal fins {d) 

 are articulated, are supported by the neural spines. A similar 

 system of bones, the interhmmals (79), afford the base for the 

 articulation of the rays of the anal fin (a). The last and smallest, 

 caudal vertebra articulates with the hypural (70), a fan-like bone, 

 which, together with the dilated hindermost neural and haemal 

 elements, supports the caudal rays (c) . 



As an example of the Chondropterygian type, a figure of the 

 skeleton of Carcharodon rondeletii, which is exhibited in the 

 Entrance Hall, is given here (fig. 43, p. 55). 



The substance of the skull is cartilage. The articulation 

 with the vertebral column is effected by a pair of lateral condyles, 

 and a central conical excavation corresponds to that of the 

 centrum of the first vertebra. The cranium itself is an undivided 



Fk. 43. 



Skull of Carcharodon. 



cartilage, with three rod-like plates forming the base of the pro- 

 jecting conical snout. As separate cartilages there are appended 

 to the skull a suspensorium (sw), a palatine (p/), mandible {md), 

 hyoid (Ay), and rudimentary maxillary elements. The suspen- 

 sorium is movably attached to the side of the skull. What is 

 generally called the upper jaw of a Shark is not the maxillary, but 

 the palatine. It consists of two simple lateral halves, each of 



