THE LAND AND FRESHWATER MOLLTJSCA OF DORSETSHIRE. 83 



CLASS II.-GASTEROPODA, OR UNIVALVES. 

 ORDER 1 . PECTINIBEANCHIATA. 

 FAMILY I. J 



Although this family is widely dispersed, it is represented in 

 Great Britain by one genus, and only one species of that genus. It 

 is herbivorous. 



NERITINA, Lamarck. 



NERITINA FLUVIATILIS, Linn., pi. 6. 



NERITA FLUVIATILIS, Pult. cat., p. 50, Rack, ed., p. 57, pi. 16, f. 



17, 18. 

 Body yellowish-grey, speckled with black above, white below. 



Shell orbicular above, the under side rather concave, solid, glossy, 

 compressed towards the spire; brown yellow with whitish zigzag 

 streaks; whorls three, body whorl occupying more than two-thirds 

 of the shell ; mouth semi-lunar ; outer lip sharp ; tuner lip flat, 

 broad, and polished; operculum semi-lunar, glossy, yellow or orange 

 colour. L.0.35. B.0.25. 



Hab. Slow rivers, and lakes which are supplied with running 

 water, or having a gravelly bed. This species ranges from 

 Finmark to Algeria and Sicily. Generally distributed. 



FAMILY II. 

 Genus I. PALUDINA, Lamarck. 

 1- PALUDINA CONTECTA, Millet^ pi. 6. 

 P. LISTERI, F. and IT. iii., p. 1, pi. Ixxi., f. 16. 

 HELIX vrviPARA, Pult. cat., p. 48, Rack, ed., p. 54, pi. 17, f. 2. 

 Body dark-grey or brown, with yellow specks. 



Shell conical, globulose, thin, moderately solid, glossy, semi- 

 transparent, brown-olive colour, with three brown bands on the 

 last whorl, which are not very distinct : also two on the two preced- 

 ing whorls, there are also very fine and closely set longitudinal 

 striae; whorls seven, very convex, the last occupying about one-half 

 of the shell ; spire pointed ; mouth oval, or almost circular and 

 slightly angular above, the outer and inner lips form a complete 

 peristome, which is purplish inside; operculum thin, with several 

 unequal concentric striae, the centre being nearest the inner lip. 

 L.1.5. B.1.S25. 



Hab. Slow rivers, canals and lakes. Pulteney gives no 

 locality, but says it is common on ponds and rivers on the 

 Potamogeton and other plants, especially in a clayey soil. 



