126 C O N C H O L G Y. 



gether, therefore it is from the refult of 

 obftrvations only I aflert it. However, 

 any land Snail will demonftrate it ; which, 

 if we did not know was a land Snail, we 

 might pofitively affirm to be one from its 

 operculum or lid ; for it is leathery, has 

 no concentric or fpiral lines, and is Ipread 

 over the mouth in fuch a manner, as even 

 to pafs over the very edges or contour : 

 whereas, on the contrary, a Bloody Tooth, 

 Nerit, or any Buccinum, can be proved to be 

 fea^Shells, by their opercula being fhelly, by 

 the work on them, and ahb by being clofed 

 within the lips or edges of the aperture, 

 and not fpread over them. 



Thefe reafons make me rejeft, in my 

 lyflem, the divifion of Shells into land, 

 river, and fea ; becaufe, for want of com- 

 mon fixed charaflers, we never can pofi- 

 tively afcertain which are which. I there- 

 fore {hall blend all Shells together without 

 fuch diftinSlions, 



' Afe^ 



