2 PERISTOMIDA. 



Hist., VI, p. IG; Lamarck, An. San. Vert., VI, pt. 2nd, p. 188;; 

 Fleming, Brit. An., p. 321 ; Brown, Illustrations Conch. Great 

 Britain and Ireland, p. 26, pi. 13, f. 45; Nerita Jluviatilis, 

 Miiller, Moll., II, p. 194; Drapernaud, Hist. Moll., p. 31, pi. 1, 

 f. 1 ; PfeifFer, I, p. 106, f. 37, 38, 39; Fleming, Edin. Ency., 

 VII, p. 82 ; lb., Brit. An., p. 321 ; Brard, p. 194, pi. 7, f. 9, 

 10, 12; Brown, Wernerian Mem., II, p. 552 ; Turton, Conch. 

 Die, p. 127 ; Neritina fontinalis, Brard, Hist. Conch., p. 196, 

 pi. 7, f« 1 1 ; Theodoxus Lutetianus, De Montford, II, p. 351 ; 

 Da Costa, Brit. Conch., p. 48, pi. 3, f. 8; Pennant, Brit. Zool., 

 IV, p. 141, pi. 88, f. 142; Donovan, Brit. Sh., I, pi. 16, f . 2 ; 

 Montagu, Test. Brit., p. 470. 



Shell suboval, subpellucid; body very large; spire extremely 

 small, oblique, and lateral, consisting of two well defined 

 volutions, and terminating in a minutely small, slightly pro- 

 duced apex ; aperture luniform ; outer lip thin, sharp at the 

 edge ; pillar lip white, flat, and very broadly reflected on the 

 columella; aperture closed by a testaceous operculum, of an 

 orange-yellow colour; whole shell covered with a brown or 

 greenish epidermis, beneath which the surface is glossy and 

 smooth, but longitudinal, minute wrinkles, are observable by 

 the aid of a strong lens ; beautifully streaked, spotted, or 

 mottled, with white and purplish-brown, deep umber, or pate 

 brown, and in some instances with spiral bands of either of 

 those colours. Length three-eighths of an inch ; breadth a 

 quarter of an inch. 



Fig. 3 represents the operculum. 



Found in many of the slow running rivers and streams of 

 Great Britain and Ireland adhering to stones, as the Thames, 

 Humber, Tyne, and Tweed in England; the LifFey, in Lough 

 Derg, and near Banacher, in the Shannon, and in some of the 

 tributaries of that river, in the County of Tipperary, and 

 Bresna in Ireland, the Grand Canal, near Clonooney, and also 

 near Dublin ; and the Forth, Tay, and Clyde in Scotland. 



Family II.— PERISTOMIDA. 



Shell conoid, or subdiscoid, with the margins of the aperture 

 united; aperture protected by an operculum; fluviatile, and the 

 animal having the power of respiring in water. 



