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of the columella, which is twisted or arched. Most of 

 the species are of a beautiful pearly substance, and 

 many of them have longitudinal ribs, (an occurrence ne- 

 ver seen in the Turbines, for which some of this genus 

 have been mistaken); the whorls of many of the species 

 are marginated, with compressed vaulted scales or 

 spines, more or less long; the aperture heart-shaped 

 and closed by an operculum. Some species have the fa- 

 culty of attaching stones, corals, and fragments of shells 

 to their exterior, as the T. agglutinans of Lamarck, 

 (T. conchyliophorus of Linnaeus). These have not been 

 particularly distinguished by Lamarck, and might with 

 great propriety form a distinct family. 



Trochus imperialis 



Trochus asperatus 



longispina 



rhodostomus 



Solaris 



spinulosus 



Indicus 



costulatus 



radians 



inermis 



pileus 



agglutinans 



calyptraeformis 



caelatus 



fimbriatus 



tuber 



brevispina 



magus 



rotularius 



merula 



stella 



argyrostomus 



stellaris 



Cookii 



