Dr. Mantell on the Ventriculites. 133 



thirteen or fourteen very strong, single or dichotomous ridges, 

 the sides of which are usually cut by numerous deep oblique 

 sulci ; the ridges are highest at the base, where they terminate 

 abruptly ; osseous base a little wider than the crown. Diameter 

 of base 3 to 4 lines. 



This tooth presents considerable variation in the proportion of 

 height to width of the base, and also in the number and rela- 

 tive thickness and complexity of the ridges ; there is no variety 

 however sufficiently striking to require particular notice or occa- 

 sion any difficulty in the identification of the species. 



It seems abundant in some parts of the Derbyshire limestone. 



(Col. Cambridge University.) 



Hybodontes. 



Cladodus Itevis (M'Coy). 



Sp. Char. Principal cone very thick, slightly oblique, its height 

 equal to half the width of the root ; secondary cones two on 

 each side, very strong, the outer largest and divaricating, 

 nearly half the length of the principal cone ; all the cones ob- 

 tusely rounded at the summit, very slightly tapering, and the 

 height of each slightly exceeding the width of its own base ; 

 base of the crown and osseous root concave ; surface of all the 

 cones smooth, highly polished. Width of crown 9 lines, height 

 of principal cone from the basal margin 5 lines. 

 This closely resembles the C. marginatus (Ag.) in size and 

 form, but the cones taper less and the species is fully distin- 

 guished by its smooth surface, destitute of the coarse longitudinal 

 plaits or striae of that or the allied species. 

 Carboniferous limestone of Armagh. 

 (Col. University of Cambridge.) 



XIII. — Dr. Mantell on Mr. Smith's "Observations " in Annals 

 of Nat. Hist, for July 1848. 



To the Editors of the Annals of Natural History. 



Gentlemen, 

 As I have neither leisure nor inclination to engage in contro- 

 versy, I shall offer but one remark on the observations of Mr. 

 Toulmin Smith. 



In the last Number of the 'Annals' (p. 49) Mr. Smith has 

 quoted certain passages from my ' Wonders of Geology' (6th edit, 

 p. 638), which he is pleased to declare are at variance with opi- 



