CRETACEOUS EORMATIONS. 55 



much as it does that of the Iguanodon from the Hythe Saurian. The medullary canal 

 is described as being very great in the tibia of the Poikilopleuron.* 



The absence of vertebrae and teeth in the Hythe specimen prevents the establish- 

 ment of a comparison of these instructive parts of the skeleton of the two extinct 

 Saurians, and the question of the dental characters of the Poikilopleuron remains in 

 the same doubtful state as it is left by M. Deslongchamps, who describes and figures 

 a detached large Crocodilian tooth from the Oolite near the village of Allemagne, as 

 corresponding in size with the remains of the Poikilopleuron. f 



M. Deslongchamps conceives it may be useful to make known these teeth at the 

 same time with his Poikilopleuron, leaving to subsequent discoveries the determination of 

 the truth or otherwise of the approximation. For the same motive I have prefixed to 

 my account of the Hythe Saurian a description of the teeth of a gigantic, and hitherto 

 unknown Saurian from the Green-sand at Maidstone, and shall append to it an account 

 of similar teeth from the Chalk Formation in Sussex, Kent, and Cambridgeshire. 



Since the bones of the extremities of Mr. Mackeson's large reptile from the Green- 

 sand afford sufficient evidence of their distinctness from the tallying parts of any 

 previously described Saurian genus, and since we have evidence as satisfactory of an 

 equally gigantic Saurian genus from the teeth which occur in the same Formation, it 

 may be allowable, for the purposes of the present record, to regard both the bones and 

 the teeth as parts of the same animal. Until, therefore, further evidence is obtained, 

 showing the Hythe skeleton to have been furnished with differently-formed teeth, or 

 the teeth from the Maidstone Green-sand to have been associated with a differently 

 constructed skeleton, I shall apply to the Hythe fossil the name of Polyptychodon, 

 under which the genus of gigantic Saurian, hitherto known only in the Green-sand and 

 Chalk strata, was first indicated, 



Polyptychodon iNTERRUPTus, Owen. Tab. X, figs. 7, 8, 9; Tab. XI; Tab. XIV, 



figs. 1 and 2. 



' Odontography,' vol. ii, p. ] 9, pi. 72, fig. 4 ; and in Dixon's ' Geology and Fossils of the 

 Tertiary and Cretaceous Deposits of Sussex,' p. 3/8. 



The majority of the specimens of the teeth of this species have been found in 

 the middle and lower Chalk or Chalk-marl : one large tooth of this species has been 



* " Le canal medullaire etait fort grand ; l'epaisseur du tissu compact, en d, est d'environ 0™' 015." 

 (Deslongchamps, ' Sur le Poikilopleuron,' 4to, p. 55.) 



"Dans ce tiers inferieure, le femur est un peu plus etendu transversalement que d'avant en arriere." 

 (Deslongchamps, loc. cit.) 



f "On a troirve, k diverses epoques, dans les carrieres du Village d' Allemagne de grandes dents, 

 toujours isolees, offrant tous les caracteres de celles des Crocodiles. J'en figure une, pi. vi, (de grandeur^ 



