4 8 4 



MOLLUSKS : GASTEROPODS. 



Fig- 4*5- 



Fig. 



Fig. 416. 



Neritina zebra, Brug. 

 Pacific. 



Fig. 418. 



Nerita ustulata, L 

 Scinde. 



Valvata tricarinata, Say. 

 United States. 



Paludina Integra, Say. 

 Western and Middle States. 



pedicels outside the tentacles. Operculum horny or 

 shelly. There are one hundred and fifty living species. 

 Fig. 4 i 7 . NERITID^:, OR NE- 



RITA FAMILY. This 

 Family contains gas- 

 teropods which have 

 the shell thick, glob- 

 ular. Three hun- 

 dred living species. 

 TURBINID.E, OR TOP-SHELL 

 FAMILY. This Family com- 

 prises gasteropods which 

 have the shell turbinated 

 and the operculum very 

 small. The shell is brilliant 

 pearly when the epidermis is 

 removed. There are about 

 nine hundred living, and as many fossil species. Marine. 

 Fig. 419- . HALIOTID,E, OR EAR-SHELL FAM- 



ILY. This Family contains gastero- 

 pods which have the shell spiral, 

 ear-shaped, or trochiform, and no 

 operculum. Haliotis is much used 

 for ornamental work. There are one 

 hundred living, and more than one 



Haltoiis tuberculata, L. * iir-i -! 



Britain. hundred fossil species. Marine. 



Trochus zizyphinus, L. Britain. 



