201 



side ; foot short, oval, with an anterior marginal groove ; head with 

 a proboscis, depressed ; tentacula remote, with the eyes on their 

 middle, beyond which they are slender ; mouth terminal, vertical, 

 without labial tooth and with a very small tongue ; a long and nar- 

 row branchia. 



Ohs. Brugui^ire adopted the name of this genus from Adanson, 

 who says, that Fabius Columna used the word to designate one of 

 the species. The following is the descriptive appellation of the 

 latter, " Buceinum tuberosum Cerithium parvum." • All the species 

 which Adanson referred to it are correctly placed, with the ex- 

 ception of the Ligar, {Turritella tcrchra, L.) and the Mesal, botli 

 of which he was aware diJBFer generically from the others. He thu;^ 

 describes the operculum of C. radula, L., and his figure corres- 

 ponds in character, " opercule exactement orbiculaire, cartila- 

 gineux, fort mince, brun transparent et marqu6 de cinq sillons^ 

 circulaires concentriques," but Blainville says it is subspiral. 

 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, tubercles and other sym- 

 metrical protuberances. Linne placed the species known to him 

 in the very different genera Murex, Trochus and Stromhus. Blain- 

 ville includes, as subgenera, Pyrena, Lam., Potamides, Brong.. 

 Pyrazas, Montf, Nerine, Def, and Triphora, Desh. The aper- 

 ture 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 collection.'; 

 become enriched, the more difficulty attends the determination of 

 of genera, and particularly of species ; the vacancies which we sup- 

 posed 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 

 in 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 his attempts to ascei'tain the 

 changes that have taken place in the surface of the globe. 



Cerithium muscarum. — Specific diaracter. White, with 

 costae, transverse stride and series of brown spots. 



16 



