GASTEROPODA. 



59 



tiful species, is seldom obtained for less than five or ten 

 pounds. 



When a section is made of a cone it will appear that 

 the sides of the internal whorls are much thinner than 

 those of the external ; it is supposed that this arises from 

 the animal reducing the thickness of these internal walls 

 by absorption, either for the purpose of giving itself more 

 room, or in order to diminish the weight of the shell. 

 They are found abundantly from shallow to deep water in 

 all tropical countries, particularly Asia ; but become more 

 rare as they approach the northern hemisphere; a few 

 species only inhabit the Mediterranean. They are gene- 

 rally found in holes of rocks and coral reefs. 



Family 4. — PLE UR O TO MA CEA. 



The animals have no snout, but a proboscis ; and the 

 tentacula are united together at an acute angle, with the 

 eyes about half way up ; the tongue on each side has a 

 row of prickles similar to those of the family 

 Conea, which are simple, and without hooks. 

 The shell is spindle-shaped, the aperture is 

 lengthened at the lower part into a canal or 

 simply notched, and the right lip has a deep 

 slit near the suture. — Marine. 



Pleurotoma. Lam. — Shell turreted or 

 fusiform ; canal straight and rather long ; right 

 lip with a slit at the upper part near the 

 suture ; left lip smooth ; operculum small, 

 sharp-pointed, and horny. Animal described 

 in that of the family. — 369 species*; also 

 fossil. 



* Reeve's Iconica. 



