The Story of the Eocks 



121 



of a decadent race of lizards, the Rhynchocephalia, whose 

 members were among the earliest of the reptiles to appear 

 upon the earth, and whose descendant differs but little from 

 the ancestral types. 



A. THE SHARK CESTRACION 

 From Pirsson and Schuchert, after Garman. 



B. THE CROSSOPTERYGIAN POLYPTERUS 

 From Dean, ' ' Fishes, Living and Fossil. ' ' 



C. THE NEW ZEALAND LIZARD HATTERIA 



From Gadow, "Amphibia and Eeptiles, The Cambridge Natural His- 

 tory, ' ' 



Band C T)y permission of the Macmillan Company. 

 Copy furnished by Conrad Lantern Slide Company, Chicago. 



Other relatives of the early sharks were the Crossoptery- 

 gians, whose descendants are found today in the Nile, Niger 

 and other African rivers. In the arrangement of the dermal 

 head plates they are suggestive of the Stegocephala or extinct 

 amphibians which nourished in the Carboniferous or coal- 



