OF CONCHOLOGY. 33 



requires, however, no argument to 

 prove it is so, to those who have taken 

 the trouble to examine the common 

 species of heterostrophe shells, which 

 daily present themselves to our notice 

 in our rural walks. Indeed, it is ra- 

 ther strange that no one of these 

 shells, whose nature is to have their 

 spires turn in the more unusual man- 

 ner, has (to our knowledge) even been 

 met with to vary from that formation ; 

 as such accidental deformities have 

 been found, in a few instances, amongst 

 those which are usually termed dexte- 

 rals, or have the more usual spiral 

 turns, and have become lusus heteros- 

 trophon shells. 



" In order, therefore, to explain 

 which way the turn of the spiral con- 

 volutions of a reversed shell takes, 

 omitting the vague signification of 

 turning to the right or left, we shall 

 observe, that the more common turn 

 of shells is with the apparent motion 



F 



