PLAGIOSTOMI 



111 



species of Corax, including G. falcatus, are cretaceous ; a few 

 are tertiary : all are extinct, 



Fig. 32. 



Notidanus Miinsteri. 

 (Upper Oolite.) 



Fig. 33. 



Corax falcatus. 

 (Chalk.) 



Fig. 34. 



Galeocerdo aduncvs. 

 (Miocene.) 



Fig. 35. 



Another form of shark's tooth, deeply notched at one mar- 

 gin, and -with the rest of the border finely denticulate, resembles 

 more that of the "topes" or gray sharks (Gcdeus, Cur.), and 

 is referred by Agassiz to the genus Galeocerdo. The species are 

 found in both the cretaceous and tertiary forma- 

 tions ; Galeocerdo aduncus (fig. 34) is from the 

 miocene of Europe and America. In the same 

 tertiary series are found the teeth of the Hcmi- 

 pristis scrra, Ag. (fig. 35). 



Odontaspis (Ag.), presents a form of tooth most 

 like that in the blue sharks {Lamnci) of the pre- 

 sent seas. Species of Odontaspis occur in the ere- Hemvprigtis 



* x serra. 



taceous and tertiary beds. The 0. Hopei (fig. 36) (Miocene.) 

 is from the London clay of Sheppy. It indicates a very 

 destructive and formidable species of shark. 



Teeth shaped like those of the white sharks 

 (Carcharias), but solid and usually of large size, 

 are referred to the genus Carcharodon. One of 

 these teeth, from miocene beds, Malta, in the Hun- 

 terian Museum, London, measures 5 inches 10 

 lines at its longest side, and 4 inches 8 lines across 

 the base. By the side of it is placed a tooth of an 

 existing Carcharias, 2 inches 3 lines at its " longest 

 side," from a shark which measured 20 feet in 

 length. If the tooth of the fossil Carcharodon bore the same 



Fig. 36. 



Odontaspis 



Hopei. 

 (Eocene.) 



