300 



PALAEONTOLOGY. 



plesiosaur has been likened to the body of a serpent con- 

 cealed in the carapace of a turtle : the neck had thirty- three 



FIG. 204. Pterodactylus crassirostris. Goldfuss. 



vertebrae, whilst in other genera of this class the numbers 

 vary from three to eight. It probably lived in still water, 

 not far from the shore. The first species is found in the 

 trias, but their greatest development was during the depo- 

 sition of the lias. They are found in the other stages of 

 the oolite, and in the chalk of New Jersey, IT. S. (Fig. 203.) 



The Pliosaurus was a gigantic reptile, intermediate be- 

 tween the two preceding genera. We know two species 

 from the Oxford and Kimmeridge clays. 



Seven species of Notliosaurus have been found in the 

 Devonian, Permian, and conchylian stages. Diacosaurus, 

 Conchiosaurus, Simosaurus, and Pistosaurus, are from the 

 mtischelkalk of Germany ; and Spondylosaurus is from the 

 oolite of Moscow. 



5th Family. The PTERODACTTLIDJE. If the Ichthyo- 



