90 PHYTOPHAGA. 



1. Paludina. Operculum horny; mouth of the 

 shell thin. 



2. Bithinia. Operculum shelly; mouth of the 

 shell thickened internally. 



3. 1. PALUDINA Lam. (Marsh Shell.) 

 Operculum horny, the nucleus rather on the inner 



side (p. 78. f. 8.); shell conoid or oblong; mouth 



roundish, slightly angular behind ; peristome united 



all round, thin. (p. 78. f. 7.) 



They are called Paludina from their being found in 

 marshes and ditches. 



The animals are viviparous, the young being 

 hatched while the eggs are in the oviduct of the 

 mother. 



The shells of the newly-hatched individuals are 

 covered with spiral bands of cilia. 



3. 1. PALUDINA vivipara. Crystalline Marsh Shell. 



(t. 8. f. 118.) Shell thin, oval, acute, volutions 



five, much inflated, with three brown bands; 



the suture deeply impressed; spire blunt mu- 



cronate. 

 Helix vivipara. Linn. Fauna Su. 529. ; List. Aug. 



t.2. f. 17.; Petiv. Mus. 84. n. 814.; Montagu, 



T. B. 386. 

 Paludina crystallina. Gray, Med. Rep. 1821, p. 



239. 

 Nerita fasciata. Mutter Verm. ii. 182. part. 



vivipara. Mutter, ii. 182. 



Cyclostoma viviparum. Drap. 34. 1. 1. f. 16, 17. 

 Paludina vivipara. Lam. vi. 173.; Nilson, 88.; 



Turton, Man. ed. 1.133. f. 118. ; Brard, 174. t. 7, 



f. 1.; Eossm. f. 66.; Desk, viii.511. 



