714 Mr. Stokes on Orthocerata. 



It may be asked, why we do not find rhyncholites in these older rocks ? but 

 I do not feel the objection to be of much importance, when I consider the 

 comparative rarity of those fossils in the rocks in which the Ammonites are so 

 numerous. 



It will not be doubted that these chambered shells belonged to the carni- 

 vorous race of Cephalopods : we know of no other remains in these older rocks 

 which can be attributed to carnivorous marine animals, except some few 

 fishes; and it is quite in unison with the other observations that have been 

 made in the natural history of organic remains, to find a great variety of forms 

 of this family existing at one period, when they were the chief agents in per- 

 forming the duties allotted to the marine Carnivora, and to find that their re- 

 presentatives in this family were subsequently confined to the forms of Am- 

 monites and Belemnites, when other creatures, such as the Saurians, were 

 created to take a part in the important task assigned to them. A similar change 

 is the appearance of carnivorous Trachelopods at a later period, on which 

 subject are some good obsei-vations first pointed out in a paper by Mr. Dill- 

 wyn, in the Philosophical Transactions for 1823. 



