352 Dr. Riley and Mr. S. Stutchbury on Saurian 



Another distinction in the Saurodon is in tlie different length of the edges, one being longer than 

 the other. 



Under these circumstances we consider our animal to be a new genus, and shall found it upon 

 its being a Lizard with alveoli in its jaws. 



We propose to designate the animal generically, from the characters of the jaw and teeth com- 

 bined, by the name of Thecodontosaurus. 



We have also two separate teeth, which differ from the preceding and 

 from each other. Fig-. 5, a single tooth -roths of an inch long and -Vths broad, 

 carinated ? laterally and finely serrated at right angles to the axis ; this tooth 

 approaches more nearly in form and serratures to the upper portion of the 

 tooth of a Megalosaurus. Fig. 4. The portion of this tooth which has been 

 preserved, is about -^^ths of an inch in length, and -rVths in breadth : the edge 

 is finely carinated, as in fig. 5. These teeth differ so much from all those of 

 Saurians witli which we are acquainted, and so greatly from each other, that 

 we are inclined to attribute them to two new animals. For the present we 

 propose to name the genus Paleosaurus, and the species, from the form of 

 the teeth, may be called P. Cylindrodon and P. Platyodon, Figs. 4 and 5. 



Vertebrce. — Plate XXIX., fig. 6, 7, and 8, natural size. 



The few vertebrae which have occurred, are so much mutilated, that we have 

 great difficulty in determining even the region of the columns, to which they 

 belonged. 



With one exception, we are not possessed of a specimen having the body 

 or annular portion in its complete form ; whilst with regard to their processes, 

 we have not a single instance of one, even in a tolerable state of preservation. 



The specific and generic characters must, therefore, with our present means, 

 be still more difficult of attainment. 



Wherever we are able to inspect the bodies of the vertebras, we observe 

 that they are concave at each end. 



In the best preserved specimens, the centre of each body is so much dimi- 

 nished in its transverse and vertical diameters (Fig. 6.) as to be reduced in- 

 feriorly and laterally to one half of the size of either end. 



In one instance, we can distinctly trace a suture connecting the annular 

 part or body with the process (Fig. 6.). In the same specimen, we have a 

 mould of the vertebral or spinal canal composed of the magnesian matrix ; and 

 it shows a very peculiar form in the upper portion of the annular element, con- 

 stituting the inferior boundary of the canal. The body of the vertebra is 

 hollowed out by a deep and narrow depression on its upper surface, so that 

 the inferior boundary of the vertebral canal would not be on one level plane. 



