FOSSIL REPTILES. 375 



animal of, at least, thirty feet in length. Many other bones 

 have been found announcing a gigantic size in plesiosaurus, 

 but M. Cuvier thinks it probable that they belonged to a dif- 

 ferent species from the Lyme skeleton. 



In fact, there are several species of plesiosaurus as well as 

 of ichythosaurus. Mr. Conybeare has characterized one by 

 the vertebrae found in the argilla of Kimmeridge. They are 

 much shorter from front to back, than those of the common 

 plesiosaurus, and as flat as draught-pieces, or as the vertebrae 

 of the ichthyosaurus, although their faces are not so concave. 

 They are recognized by their sutures, their facets, and, parti- 

 cularly, by the two small holes of their lower face. 



Mr. Conybeare has named the species which furnished the 

 skeleton of Lyme, plesiosaurus dolichodeirus, or long-necked 

 plesiosaurus, and that whose vertebrae came from Kimmeridge, 

 plesiosaurus recentior. 



But other species appear to have existed. M. Cuvier re- 

 ceived a cervical vertebra which was found at Boulogne, and 

 apparently in the oolite. It is distinguished by a blunt longi- 

 tudinal crest in its lower face between the two small holes, and 

 certainly must have come from a different species from the 

 two former. It is provisionally named by M. Cuvier, plesio- 

 saurus carinatus. 



Some other cervical vertebrae from Honfleur were in the 

 Baron's possession, longer in proportion, and flatter under- 

 neath, than their correspondents of Lyme. But the difference 

 is not much to be rested on. 



But the Baron considers certain vertebrae of the tail, which 

 he received from Auxois, as belonging to a distinct species. 

 Their body is not cylindrical, but pentagonal. 



He comes to a similar conclusion relative to a vertebra from 

 the coast of Calvados. It is triangular, like some of those of 

 -the animal of Maestricht, that is, flat and broad below, growing 

 more slender towards the top, and presenting on the sides of 

 Us lower face, its transverse apophysis. 



