GASTEROPODA : PALUDINIM;. 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^:, OR WENTLE-TRAP FAMILY. This 



Family embraces gasteropods which have the shell tubu- 



Fig. 409. 



i 



Fig. 410- Fig. 411. 



Scalaria pretiosa, Lam. Vermetus lumbricalis, Gm. 



Two thirds. China. West Indies. 



Turritella imbricata, 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- 



, rr^, . i i T .. ". 71 . Lacuna vincta, 



culum horny. They inhabit Litonna paiu- 



, ata. Say. 



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^:, 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 



