42 FOSSIL REPTILIA OF THE 



it might have coexisted with a femur in which a small medullary cavity had been 

 established. Compression proves nothing, however, as against the cancellous tissue 

 of the centre of a bone : the force that would squeeze the medullary shaft of a 

 Crocodilian femur 4 feet long, to a thickness of 3 or 4 inches, would overcome 

 any resistance that the loose spongy texture of a Cetiosaurian bone would offer. 

 Moreover, the shorter diameter of the humerus, referred by Dr. Mantell to 

 Pelorosatirus, is but 4| inches ; and the medullary cavity there, is most patent 

 and perfect : such a cavity could scarcely have escaped the notice of so close 

 an observer as the late Mr. Hugh Strickland, if it had really existed in the long- 

 bone from Enslow Bridge, now in the Geological Museum at Oxford, and referred to 

 the genus Cetiosaurus. 



The satisfactory proof of the existence of remains of a huge species of Wealden 

 Saurian distinct from Ignanodon, Hylceosauriis , Megalosaurus, and Cetiosaurus, is 

 afforded by the vertebra;, one of which is figured, of the natural size, in Tab. XI. 

 For this genus and species the name of Pelorosaurus Conybearii, may be most 

 conveniently retained : most properly so, indeed, if ulterior discoveries should prove 

 the hollow humerus to belong to a reptile with the Pelorosaurian type of vertebra. 



In the descriptions of the vertebrae from the Wealden given in my ' Report ' 

 of 1841, and in the figures of them now published, the foundations, at least, may 

 be laid for rightly reconstructing the huge and strange Reptilia to which they 

 severally belonged. 



Tooth of a large carnivorous Wealden Reptile. 



A fossil tooth of a large reptile was discovered, some years ago, in the Wealden 

 Clay of Brixton Bay, Isle of Wight, which differs from the similarly sized teeth of 

 Jguanodon and Megalosaurus, and, therefore, most probably belongs to either the 

 Cetio- or Pelorosaurus. 



The crown of this tooth, measured along the greatest extent of enamel, is 2 inches : 

 about 1 inch and 5 lines of the fang is continued beyond the crown. The fang is 

 Hubcylindrical at its broken base, becomes compressed as it approaches the crown, 

 and this expands, with a diminution of thickness, as it extends from the fang, for 

 about one third of the length, where two opposite trenchant margins begin; after which 

 it gradually contracts to a point. 



The extreme breadth of the crown measures 1 inch ; the thickness is 8 lines. 

 On one side the crown is unequally convex ; on the opposite side, at the apical two 

 thirds, it becomes a Httle concave : one margin is gently convex, the other is very 

 slightly concave. The convex side of the crown is covered by smooth enamel, which 

 forms four low ridges on its most prominent part, and terminates inferiorly, by a 



