TURBO TURBAN SHELL. 103 



the boundaries by which they are separated ; the 

 mouths of the Trochi gradually losing the 

 angular, and assuming the orbicular form ; 

 whilst many species of the Turbines exhibit a 

 very imperfectly circular aperture.* Both names 

 also imply any thing that whirls round ; and the 

 shells in each genus agree in their conical form, 

 and in shewing no indication of an increase in 

 growth, after the first formation. Besides, this 

 general resemblance in their appearance, the 

 animals are nearly allied in their habits. The 

 marine species are found on rocks and craggy 

 shores, or on the sand, when detached by *a 

 storm from their customary abode. 



There are several species of Needle or Screw- 

 shell among the Turbines ; they are distinguished 

 by their circular mouth, from those of a similar 

 form in other genera ; their shape is that of a 

 well-proportioned spire, formed by thirty or 

 forty whorls, gradually tapering from the base 

 to the apex, and terminating in a fine point. 

 There are upwards of seventy species of Turbines 

 among British shells, and several of them are 

 terrestrial. t One called Turbo Fasciatus, is 

 found so abundantly in a part of Cornwall, that 

 it is impossible to take a step without crushiing 

 numbers. It is the prevailing opinion that they 

 contribute much to fatten sheep ; they spread 

 themselves over the plain and hill near Whitsand 

 Bay, Cornwall, and the sheep which browse on 



* Turbo, the Latin for a whirlwind ; trochus, a top. 



