434 VERTEBRATE LIFE AND ORGANIZATION 



F.gure 22.7 A group of cartilaginous fishes. A, A male dogfish, Sqiialus acanthias; 

 B the sawfish Pristis: C, the sting ray, Dasyatis: D, the ratfish, Chimaera. (A, modified 

 alter liigelow and Schroeder; C, courtesy of Marine Studios; D, from Romer after Dean ) 



fishes. The nature of the skeleton gives the name to the class; Chon- 

 drichthyes means cartilaginous fishes. 



The upper and lower jaws are formed from the mandibular arch 

 and are provided with a great many sharp, triangular teeth which 

 evolved as a modification of bony scales. The resemblance between a 



