295 



as the most beautiful of the class which comprehends 

 the spiral univalves; among them are many of extreme 

 rarity, and of remarkable elegance in the symme- 

 try of their form, diversity of marking, and richness 

 of coloring matter. They constitute a very natural 

 and easily distinguished association, including an im- 

 mense number of species. The most remarkable and 

 distinguishing character of this genus is the shells hav- 

 ing the whorls of the spire compressed and rolled over 

 each other, the outer one being entirely visible, and 

 the upper edges of the previous evolutions only seen 

 with a suture or groove between them; these spiral 

 elevations are termed the spire, which is sometimes 

 nearly flat, convex, more or less produced, and occa- 

 sionally even slightly concave ; the extremity of the 

 whorls coronated, smooth, or tuberculated. It results 

 from the form of the shell, and the spiral cavity (which 

 contains the animal) being compressed in its whole 

 length, and the largest part nearest the spire, that they 

 may be strictly called turbinated shells, attenuated to- 

 wards the base; the aperture is narrow, effuse at the 

 base, never dentated ; the outer lip smooth and sharp. 



Lamarck has divided this genus into two sections: 

 the first Including the coronated Cones; the second, 



