144 MISCELLANEA. 



forming a solid frame-work actually capable of being preserved, 

 so far as the union of one vertebra to another is concerned, after 

 the removal of the whole external cartilaginous covering. 



This being the case, the vertebrae of such fishes maybe looked for in 

 a fossil state, and there is as much probability of finding them as the 

 teeth and bony spines which are generally supposed to be the only 

 hard parts. This is the more important, since it appears that the teeth 

 and bony spines alone afford no sufficient measure of the dimensions 

 and proportions of the animal. Thus, from the size of the dorsal 

 spine of a shark figured by M. Agassiz, it was concluded that the 

 animal must have been of very large size, whereas it appears from 

 the comparison of some vertebrae evidently belonging to the same 

 individual, that it could not have exceeded two feet in length. 

 Other instances of the same kind might be mentioned, so that the 

 attention of collectors ought to be carefully directed to every ap- 

 pearance of vertebrae in localities where the remains of carti- 

 laginous fishes occur, and specimens compared even when there 

 would appear scarcely a possibility of the teeth and spines being 

 referable to the same species as these rarer fossils. — See Trans- 

 actions of the Royal Society of Edinburgh, vol. xv. p. 643. et 

 seq. 



