PERISTOMIDA. 7 



33, pi. 1, f- 14; Turbo fontinalis, Montagu, Test. Brit., p. 348, 

 pi. 22, f. 4 ; Brown, Wemerian 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. 



FitT. 16, 17, pi. I, 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. IB, 19« 



Valvata cristata, Muller, 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, Wemerian 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 umbilicate 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. 



