352 



cerning the fplral turns of a hderqfi'oplie {heW; fome 

 call it from right to left, others vice veifa, from left to 

 rioht. 



Every conchologifl, knows, that moft convoluted fliells 

 turn one way, and that there are a few fpecies which are 



heteroclltical, or invariably turn contrpry to the ufual 

 manner : fome indeed have doubted, whether this is a 

 permanent cliarafter ; there requires, however, no ar- 

 gument to prove it is fo, to thofe who have taken the 

 trouble to examine the common fpecies of heteroftrophe 

 fhells, which daily prefent themfelves to our notice in 

 our rural walks. Indeed, it is rather (Irange, that not 

 one of thefe fliells, whofe nature is to have their fpires 

 turn in the more unufual manner, has (to our know- 

 ledge) ever been met with to vary from that formation ; 

 as fuch accidental deformities have been found in a few 

 inflances, amongfl: thofe which are ufually termed dex- 

 trals, or have the more ufual fpiral turns, and have be- 

 come lufus hetcrcjirophon fliells. 



In order therefore to explain, which way the turn of 

 the fpiral convolutions of a reverfed fliell takes, omitting 

 the vague fignification of turning to the right or left ; 

 we fliall obfcrve, that the more common turn of fliells ig 

 with the apparent motion of the fun, or as the index or 

 hand of a clock moves. 



But in order to be more clearly underftood; let us 

 compare the fpiral volutions of a fliell to a common 



cork- 



