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 lavis (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 w^idth 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- 



