PLAGI0ST0M1. 



133 



a fossil from Sheppy (fi 

 " vitrodentine," and the 

 " vasodentine " form- 

 ing the body of the 

 tooth. With these fos- 

 sil teeth of sharks are 

 found, though spar- 

 ingly, in both the cre- 

 taceous and tertiary 

 beds, petrified bodies 

 of vertebrae, shewing 

 by their extreme short- 

 ness in comparison 

 with their breadth, by 

 their bi-concavity, and 

 the fissures on the ex- 

 ternal surface (as 

 shewn on the lower 

 figure of cut 52) that 



51), shewing the outer hard layer of 



Fig. 52. 



The upper figure is a front 

 view, the lower one aside view, 

 of the body of a vertebra of a 

 Shark, Lamna or Odontaspis. 

 (London clay, Sheppy.) 



Fig. 51. 



Magn. section of a tooth of a Shark 

 [Lamna). 



they belonged to a shark closely allied to the Porbeagle 

 {Lamna, Cuv.) 



