PERISTOMIDA. 7 



33, pi. 1, f- H; Turho fontinalis, Montagu, Test. Brit., p. 348, 

 pi. 22, f. 4 ; Brown, Wernerian Mem., II, p. 522 ; Lymnea 

 fontinalis, Fleming, Edin. Ency., VII, p. 78; Turbo thermalis, 

 Dillwyn, p. 852. 



Shell thin, subpellucid, horn-coloured, smooth, with fine 

 spiral striae throughout, and a few obscure, concentric lines of 

 growth ; length and breadth nearly equal ; body very large, 

 much inflated, with a deep central umbilicus at its base ; spire 

 small, short, consisting of four tumid, deeply defined volutions ; 

 aperture orbicular ; peristome thin, the inner lip slightly attach- 

 ed to the body volution. Length little more than a quarter of 

 an inch. 



Common in rivers, canals, ponds, and lakes in Britain, and in 

 ditches in the Curraghs, Isle of Man. 



Fig. 16, 17} pi. Ij is a permanent variety, with the spire more 

 produced, and the volutions somewhat scalariform ; found at 

 Clonoony, King's County, Ireland. Mr. Thompson mentions a 

 variety found by Edward Waller, Esq., at Finnoe, County of 

 Tipperary, the volutions of which appear angular from being 

 spirally cut. 



2. Valvata cristata, pi. I, f. 18, IQ- 



Valvata cristata, Miiller, Verm., p. 198; Fleming, Brit. An., 

 p. 286 ; Alder, Mag. Zool. and Bot., II, p. 116; Thompson, 

 Ann. and Mag. Nat. Hist., VI, p. 18; Brown, Illust. Conch., p. 

 28, pi. 14, f. QQ, 67 ; Valvata spirorbis, Drapernaud, p. 41, pi. 

 1, f. 32, 33; Turton, Man., p. 131, f. 115; Brard, p. 187, pi. 6, 

 f. 15, 16; Turbo cristatus, Maton and Racket, Linn. Tr., VIII, 

 p. 169; Brown, Wernerian Mem., II, p. 522; Helix cristata, 

 Montagu, Test. Brit., p. 460, pi. 1, f. 7, 8. 



PI. I, f. 20, represents the young shell, Valvata minuta, of 

 Drapernaud, pi. 1, f. 36, 37, 38; Turton, Man., p. 132, f. 117. 



Shell discoidal, consisting of four cylindrical volutions, flat- 

 tened above, and umbiHcate beneath ; exposing nearly all the 

 inner volutions, these are slightly striated transversely; aperture 

 quite orbicular, attached to but not interrupted by the body 

 volution ; peristome as thick as the other parts of the shell, and 

 slightly oblique. Diameter one-tenth of an inch. 



Found in canals and ditches in Britain, and is a very common 

 species in almost all parts of Ireland. 



