482 



MOLLUSKS : GASTEROPODS. 



Fig. 402. 



Sigarciiis haliotoides, L. 

 West Indies. 



Fig. 404. 



Fig. 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- 

 =d, 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. 46. species are marine, estuary, or fresh- 



water. The living species are two hun- 

 dred, and the fossil six hundred. 



Fig. 407. 



Fig. 408. 



elc g antissi,na, 



Gmei. 



doiobrata, 

 West indies. 



Mont ' One 



Cerithium nodolositm, Brug. 



One half. Molucca. Melania. Western States. 



lo. Southern States. 



. - - This Family comprises gasteropods 

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



