54 Saiirocepliahcs Leamcx. 



p. 331, 1824. Both these relics evidently belonged to animals 

 allied to the genus Ichthyosaurus, of Conybeare ; but which 

 approach, in their organization, more nearly to the fish than to 

 the lizard. The specimen described by Dr Hays, in the Tran- 

 sactions of the_ American Philosophical Society, possesses the 

 following characters in common with the Saurocephalds lanci- 

 formis : the bodies of the teeth are in close contact throughout, 

 the nerves and vessels of the teeth passing on the inner side of 

 the alveolar processes. The inferior series of teeth entering 

 the cavities of the superior directly in the centre, in the process 

 of shedding ; the inferior series are completed before they en- 

 ter the superior, the dental serrature of the superior and infe- 

 rior jaws closing like incisors. In both also, there exists a lon- 

 gitudinal groove along the mesial aspect of the jaw-bone, di- 

 rectly below the alveolar margins, though this groove is not so 

 evident in the S. Leanus ; but it must be remarked that this 

 species was not more than one-half the size of the S. lanci- 

 Jbrmis. 



In all these particulars of organization, both species differ 

 from the Ichthyosaurus and Plesiosaurus, and from the Saurian 

 order in general. 



The S. Leanus, we find, on comparison, to be characterized 

 as a distinct species from the S. lancjformis, by the greater 

 acuteness of the teeth, by their greater comparative length, but 

 particularly by their curvature ; they are also slightly com- 

 pressed at their inner face. 



In both descriptions of these different specimens, it is stated 

 that " the bodies of the teeth are placed close together ;" which 

 would seem to imply that their exists no " separate and dis- 

 tinct aveoli."" But as the author of the paper on the S. lanci- 

 formis was not privileged to dissect the relic, he may have been 

 mistaken in this point, a question which he is willing to cede 

 as one of little importance in the present instance, as the state- 

 ment was only made to convey an idea of the close approxima- 

 tion of the bodies cf the teeth. 



Dr Hays would appear to entertain different opinions on this 

 point, and although he states that distinct alveoli do exist in 

 both specimens, yet has made a new genus for his animal un- 

 der the name " Saukodon,'" which he subsequently altered to 



