482 



MOLLUSKS : GASTEROPODS. 



Fig. 402. 



Sigaretus haliotoides, L. 

 West Indies. 



Fig. 404. 



F>g- 403- the operculum horny. 

 There are two hundred 

 and fifty living, and 

 three hundred and fifty 

 fossil species. Marine. 

 PYRAMIDELLID^E. 



Natica triseriata, Say. _,, , . 



Coast of New England. This Family comprises 

 gasteropods which have 

 the shell spiral, turret- 

 ed, and the aperture 

 small. The living spe- 

 cies are about two hun- 



dred > and the fossil 



Fig- 405- 



i 



Pyramidella elegantissima, 



doiobrata, Mont One half ' Britain ' three hundred ; all ma- 



Gmel. West Indies. r j ne< Many of the fa? 



sil species are gigantic compared with those now exisf'.ng. 

 CERITHIAD^E. This Family contains gasteropods 

 which have the shell spiral, elongated, many-whorled, 

 aperture channelled in front, the lip generally expanded 

 in the adult, and the operculum horny and spiral. The 

 Fig. 4 o6. species are marine, estuary, or fresh- 



water. The living species are two hui> 

 dred, and the fossil six hundred. 



407. 



t Cer^thi^^m nodolosum, Brug. 



One half. Molucca. Melanin. 



Fig. 408. 



Western States. 



Southern States. 



MELANIAD^:. This Family comprises gasteropods 

 which have the shell spiral, turreted, aperture often ch?n- 



