352 



ILLUSTRATED ZOOLOGICAL NOTICES. 



an approximation to that of the crag Carcharias, but it differs 

 widely in its relative proportions, and in the presence of late- 

 ral denticles. — Its robust form, and the great extent of surface 

 by which it was implanted in the jaw, indicate its having been 

 an organ of prodigious power. Its thickness is about equal to 

 half its width, as seen by the section, fig. 42. That of Carcha- 



rias megalodon is only in the proportion of 1 to 4. I am aware 

 that the teeth in the existing species of Carcharias differ con- 

 siderably in form, according to the position which they occu- 

 py in the jaw; but the above proportions will be found to 

 hold good through a series of specimens, and may therefore 

 be regarded as depending upon generic distinction. The 

 edges of the teeth in Otodus are perfectly free from serrations, 

 and the crag specimens of Carcharias appear so, but in the 

 latter their absence depends upon attrition. Some of the 

 squaloid teeth figured in Moreton's Synopsis of the cretace- 

 ceous fossils of the United States, probably belong to the 

 present genus. 



43 



m 



Figure 43 is a silicified zoophyte from the Kentish chalk, 

 which a Cidaris appears very snugly housed, with its 



