WEALDEN FORMATIONS. 13 



' Illustrations of the Geology of Sussex,' 1827, as a lumbar vertebra of the Megalosaurus. 

 But in the ' Geology of the South-east of England,' the same author, speaking of this 

 vertebra, observes, " It cannot, I now think, be separated from those figured in the same 

 plate as belonging to a Crocodile ;" p. 297, note. The body of the Megalosaurian vertebra 

 has a pretty deep, longitudinal depression between the neurapophysial suture, wanting 

 in the Tilgate vertebra here described. This, however, is not the only distinction ; 

 below the depression the centrum of the Megalosaur swells out, and is as convex 

 below as it is laterally in the transverse section, so that the outline of a transverse 

 section would describe five sixths of a circle ; a similar section of the vertebra of 

 Suchosaurus would be triangular, with the apex rounded off. The Megalosaurian 

 vertebra is more contracted at the middle, and swells out near the articular ends, 

 surrounding those articulations with a thick convex border ; in Suchosaurus the lateral 

 meet the marginal surfaces at a somewhat acute angle ; but the silky striated surface of 

 the Suchosaurian vertebra, and the smooth and polished surface of the Megalosaurian 

 one, would effectually serve to distinguish even fragments from the middle of the body 

 of each. 



The following are dimensions of the vertebra of the large Wealden Crocodilian above 

 described : 



No. 138. 

 Inches. Lines. 

 Antero-posterior diameter of the body . . . . . 3 10 

 Vertical diameter of its articular end ..... 3 2 



Transverse diameter of its articular end ..... 2 9 

 Transverse diameter of the middle of the body .... 2 



The fossil teeth from the Wealden (PL IV, figs. 5, 6), which I provisionally associate 

 with the foregoing vertebra, approach by their more slender and acuminate form to the 

 character of those of the Gavial, but differ from the teeth of any of the recent species of 

 that genus of Crocodilians, as well as from those of the long and slender-snouted 

 extinct genera {Teleosaurus, Steneosaurus, &c). The crown is laterally compressed, 

 subincurved, with two opposite trenchant edges, one forming the concave, the other the 

 convex, outline of the tooth. In the Gavial the flattening of the crown and the situation 

 of the trenchant edges are the reverse, the compression being from before backwards, 

 and the edges being lateral. 1 The tooth of the Suchosaur thus resembles in form that of 

 the Megalosaur, and perhaps still more those of the Argenton Crocodile ; but I have not 

 observed any specimens of the Wealden Crocodilian teeth in which the edges of the 

 crown were serrated, as in both the reptiles just cited. The teeth of the Suchosaur also 

 present a character which does not exist in the teeth of the Megalosaur, and is not 



1 The tooth attributed by M. Deslongchamps (' M^moires de la Societe Linneenne de Normandie,' 

 vol. vi, p. 39) to the Poikilopleuron agrees in form with those of the Gavial, and differs in the characters 

 cited in the text from those of the Suchosaurus. 



