n 



iheni to be prcfervcd without trouble, no brancli of 

 natural hiflorv lias been more fouc^ht after. 



If it \vcre poITible to add to the defcription of each 

 {heli, that of the hiflorv of tlie animal inhabitant, it 

 would, mod undoubtedly, have been of great importance 

 with refpeft to their arrangement: fuch indeed has been 

 partially attempted, but if we confider the difficulty of 

 obtaining the greater proportion of fliells in a recent, 

 or living flate, we flrall at once perceive the impoffibi- 

 biiity of claffing them by the animal. 



Great as the difficulty may be, to define the nu- 

 merous fpecies according to the Linncean, or any other 

 method, by the order, fituation, and number of teeth, 

 and formation of the hinges, in bivalves; and the ftruc- 

 ture of the mouth, or aperture, in univalves; yet we 

 believe it is lefs perplexing, than it would be by the 

 animal itfelf, from the impoffibility of invcfiigating by 

 diffistlion, the anatomical parts of the more minute 

 fpecies : fo that upon the whole, it mufl be confeffisd, 

 though arbitrary, the only, method of throwing ffiells 

 into divifions or genera is, by their form and flru61:ure. 



a 



Varioushave been the attempts of different authors 

 with regard to fyftematic arrangement, but ^^e do not 



think 



