matque de cinq sillont> circulaues conceniriques,' but 

 Blainville says, it is subspiial. They are Marine and 

 crawl upon the mud, feeding upon small animals. 



These shells are generally elongated cones, beautifully 

 decorated with regular series and bands of granules, tuber- 

 cles and other symmetrical protuberances. Linne placed 

 the species known to him, in the very different genera 

 Murex, Trochus and Strombus. Blainville includes, as 

 subgenera, Pyrena, Lam., Potamides, Brong., Pyrazus, 

 Montf., Nerine, Def., and Triphora, Desh. The aperture 

 of the two latter have a complicated appearance, and the 

 others are altogether destitute of canal. 



Numerous recent and still more fossil species have been 

 described, chiefly by Lamarck, who remarks, that the 

 more our collections become enriched, the more difficulty 

 attends the determination of genera and particularly of 

 species ; the vacancies which we supposed to be natural 

 limits, become proportionally filled up. The difficulty he 

 experienced in fixing the character of each species of 

 Cerithium led him to the Conclusion, that it is principally 

 m this genus that this fact is the most evidently shown 

 because the collections abound in these shells. The study 

 of these shells is very important to the geologist in hi& at- 

 tempts to ascertain the changes that have taken place m 

 the surface of the globe. 



