THECODONTIA. 279 



modification of dental form by the term Cladyodon* He 

 subsequently received other specimens of the teeth character- 

 izing this genus, which may be described as being two-edged, 

 sub-compressed ; the sides more or less convex ; the edges 

 more or less sharp, and frequently finely serrate ; the crown 

 slightly bent sidewavs, the inner side towards the mouth- 

 cavity. The teeth are sometimes lancet-shaped, through con- 

 vergence of the edges towards point ; sometimes through one 

 edge being convex and the other concave, the crown is slightly 

 curved or sickle-shaped ; sometimes, through use, the point is 

 blunted. The enamel is very thin, smooth, shewing under 

 the lens a slight longitudinal striation, forming wrinkles. 

 The dentine is disposed in concentric layers ; it is not laby- 

 rinthic ; the base of the tooth shews a conical pulp-cavity. 

 These teeth indicate a Saurian about ten feet in length. 



The writer cannot discern any generic, or even good specific 

 distinctions, between the teeth of Cladyodon, from the War- 

 wickshire keuper, and those of Belodon from the Wirtemberg 

 keuper. Both are nearly allied to the thecodonts of the 

 Bristol conglomerate. 



The two following genera are referred provisionally and 

 with doubt to the present order : — 



Genus Bathygnathus, Leidy. 



Sp. Bathygnathus borealis, Leidy. — Allied to the Cladyodon 

 by the shape of the teeth is the Saurian from the new red 

 sandstone of Prince Edward's Island, North America, the 

 generic and specific characters of which have been deduced 

 by Dr. Leidy f from a portion of lower jaw, containing seven 

 teeth, but with interspaces from which others have been lost. 

 The depth of the dentary bone is five inches ; a peculiarity 



* Reports of the British Association, " Brit. Fossil Reptiles," 1841, p. 155. 

 (See fuller descriptions, with figures, in Odontography, pi. 62, A, fig. 4, «, b.) 

 f Journal of the Academy of Sciences, Philadelphia, vol. ii., p. 327, pi. 



