422 



BRITISH FOSSIL REPTILES. 



Streptospondylus — of large Wealden reptiles equally distinct from those originally 

 made known by Buckland and Mantell. 



The tooth in question may, 

 very probably, belong to either 

 Cetiosanrus or Pelorosaurus. Fu- 

 ture discoveries of teeth or of jaws 

 with teeth, associated with the 

 characteristic vertebrae of one or 

 other of these large reptiles, will 

 determine this question. 



The tooth here described was 

 first made known to geologists, 

 and figured by Dr. Thomas Wright, 

 F.G.S., an indefatigable explorer 

 of the geology and fossils of the 

 Isle of Wight, in a paper on the 

 Palaeontology of the Island, in the 

 ' Annals and Magazine of Natural 

 History' for August, 1852. 



Tooth of large Wealden Reptile. — Veliosaurm or Pelorosauros (?). 



Genus — Poikilopleuron. Eudes-Deslongchamps. 



This genus was first proposed, under the above name, by the accomplished Pro- 

 fessor of Natural History in the Lyceum or University of Caen, Normandy, in his 

 description of portions of a fossil skeleton of a Crocodilian reptile discovered in the 

 oolitic quarries near that town. This reptile was distinguished from the Cetiosanrus 

 by the more complete protection afforded to the abdominal cavity through the greater 

 development of the posterior ribs, and, as the author then believed, by the greater 

 diversity of form presented by the whole series of ribs, a peculiarity which suggested 

 the generic name.* Perhaps the most truly distinctive character of this genus, so 

 far as its organization is known, is the texture of the bones, and especially of the 

 vertebral centrums, which show unusually large cavities in their substance, with a 

 very compact outer crust, polished externally, and recalling the character of the 

 skeleton in the Pterosauria. It is this character which has led me to conclude that 

 a species of the genus Poikilopleuron has left its remains in the formations of the 

 Wealden period. 



* rioniXos, varied; TrXcvfjov, rib. 



