UNIVALVE MOLLUSCANS. 



priate food. Did all feed upon the same sub- 

 stance there would be a universal struggle, 

 unless indeed, the entire variety of the sub- 

 marine botanical world was done away, and 

 one homogeneous article provided, in such 

 quantity as to be a sufficient supply for all. 

 But further, doubtless, different organizations 

 and forms could not be maintained upon the 

 same pabulum, and therefore different creatures 

 required different articles of food, or different 

 parts of the same article. Here was a mutual 

 office the numberless vegetable productions 

 require to be kept within due limits, and there- 

 fore the functions of the aquatic animals is to 

 maintain them in due relative proportions. Was 

 the ocean and all its streams planted as now, 

 and there were no animals of any description to 

 keep in check its vegetable productions, they 

 would all in time grow up and choke the rivers 

 and gradually raise the bed of the ocean till 

 there would be no more sea. 



Having considered the plant-devouring Tra- 

 chelipods, I shall say something next upon the 

 carnivorous or predaceous ones, which form the 

 great body of large marine shells, and those 

 which most ornament our cabinets, for to this 

 tribe belong the Cowries, 1 Cones, 2 Mitres, 3 



Cyprcea. ~ Conus. 3 Mitra. 



