TURBO TURBAN SHELL. ]03 



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 th^r 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. 

 One called Turbo Fasciatm, is found so abund- 

 antly in a part of Cornwall, that it is impossible 

 'to take a step without crushing 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 the short herbage, 



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



