Dr Knox on the size of the Teeth of Sharks. 17 



drawing of the tooth, and its various measurements, which 

 are as follows : 



Dimensions of the Fossil Tooth. 



The greatest breadth of the part covered with ena- In. Lines. 



mel, measured towards the base, is, 2 6 



The length measured on the enamel of the concave 



part of the tooth, - - - - 2 3 



Length measured on the convex face, - -23 



The jaws of a shark killed on the coast of Africa were 

 presented to me by a friend ; he, at the same time, informed 

 me, that the animal from which these were taken measured 

 twenty-seven feet. Now, the dimensions of these teeth are 

 as follows : 



In. Lines. 

 Greatest breadth as above, - 1 §4 



Length of the sides, - 2 J 



Length of the centre, - - 1 c^ 



I have found it difficult to calculate exactly the difference 

 in length and breadth of these teeth, nor do I deem any nice 

 admeasurements of much moment, for I think it evident that 

 we cannot determine, with any precision, the dimensions of a 

 fossil animal, by instituting a comparison between its teeth 

 and those of similar species now existing. But, considering the 

 tooth described by M. Faujas St Fond, as being f of an inch 

 longer, which is the case only in certain of its dimensions, we 

 should have, for the length of the animal to which it belong- 

 ed, about thirty feet, instead of fifty. 



In this way the fifty feet shark of St Fond may probably 

 be reduced to thirty, and the seventy-nine feet shark of La- 

 cepede to forty-three ; dimensions sufficiently large, it is true, 

 to affect us with astonishment. It would be rash, however, 

 to conclude, that because sharks approaching antediluvian 

 dimensions are but seldom found in the present day, it there- 

 fore follows, that even they have partaken of the universal di- 

 minution in the size and bulk of all postdiluvian animals, — for 

 we know that sharks, in those days, had at least one ene- 

 my less than at present, viz. man, the common enemy to all 

 that lives. 



vol. v. NO. I. JULY 1826. b 



