434 BRITISH FOSSIL REPTILES. 



The present vertebra is alluded to at p. GO, and figured at pi. ix, fig. 11, of Dr. 

 Mantell's ' Illustrations of the Geology of Sussex,' 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. Fig. 8, PI. 9 

 (Tilgate Fossils) is, however, a caudal vertebra of the Getiosaiirus. The body of the 

 Megalosaurian vertebra has a pretty deep, longitudinal depresssion belowr 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 Suchosunrus would be triangular, with 

 the apex rounded off. Tlie 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 (PI. 5, fig. 4), which I provisionally associate 

 with the foregoing vertebree, approach by their more slender and acuminated form 

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

 species of that sub-genus of Crocodilians, as well as from those of the long and 

 slender-snouted extinct genera, called Teleosauriis, 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.* The tooth of the Sucho- 

 saur thus resembles in form that of the Megalosaur (PI. 5 fig. 5), and perhaps still 

 more those of the Argenton Crocodile ; but I have not observed any specimens of the 

 Wealden teeth in which the edges of the crown were serrated, as in both the reptiles 



* The tooth attributed by M. Deslougchamps to the Poikilupleuron agrees in form with those of the 

 Gavial, and differs in the characters cited in the te.Yt from those of the Suchosaurus. 



