GASTEROPODA: PALUDINID.E. 483 



nelled or notched in front, and a dark thick epidermis ; 

 operculum horny and spiral. They inhabit fresh waters. 

 There are five hundred living species. Figs. 407, 408. 



TURRITELLID^E, OR WENTLE-TRAP FAMILY. - This 



Family embraces gasteropods which have the shell tubu- 



Fig. 409. 



Fig. 4 



Scalaria pretiosa, Lam. Vermetus lumbricalis, Gm. 



Two thirds. China. West Indies. 



Turritella imbricate, L. 

 West Indies. 



lar or spiral, and the upper part partitioned off; all ma- 

 rine. There are two hundred living and three hundred 

 fossil species. 



LITORINID.E, OR PERIWINKLE FAMILY. This Family 

 contains gasteropods which 



Fig. 412. 



have the shell spiral, turbi- 

 nated or depressed, the aper- 

 ture rounded, and the oper- 

 culum horny. They inhabit 

 the sea near the shore, and 



feed on algae. The living species are more than three 

 hundred, and the fossil more than two hundred. 



PALUDINID.E, OR RIVER-SNAIL FAMILY. This Family 

 embraces fresh-water gasteropods which have the shell 

 conical or globular, and covered with an olive-green 

 epidermis ; tentacles long and slender, and eyes on short 



