482 



MOLLUSKS : GASTEROPODS. 



Fig. 402. 



Sigaretus haliotoides, L. 

 West Indies. 



Fig. 404- 



Fi g . 405. 



Fig. 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 over 

 three hundred ; all ma- 

 rine. Many of the fos- 

 sil species are gigantic compared with those now existing. 

 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 hun- 

 dred, and the fossil six hundred. 



Fig. 407. 



Fig. 408. 



Pyramidelladolobrata 



Gmei. West indies. 



^' 



Cerithium nodolosum, Brug. ^^ j Southern States. 



One half. Molucca. Melania. Western States. 



MELANIAD^:. This Family comprises gasteropods 

 which have the shell spiral, turreted, aperture often chan- 



