26 MOLLUSCA. 
brown, beneath which the shell is often prettily mottled, che- 
quered with brown and white, or covered with zig-zag markings, 
and banded in some instances. 
This species is common on most of the British and Irish 
coasts; adhering to stones and sea weed, between high and low 
water-mark. 
Fig. 22 represents the shell in its young state. 
Genus 33.—NeEr1TINA.—Lamarck. 
Shell thin, external surface generally smooth, and frequently 
covered with a strong, horny epidermis; spire mostly very short, 
sometimes nearly concealed, and at others obsolete; aperture 
semicircular; outer lip plain, sharp, and destitute of teeth or 
crenulations internally, but within the lower region of the aper- 
ture, it is provided with a somewhat elongated, transverse pro- 
minence, which seems the fulcrum for the articulation of the 
operculum ; inner lip flattened, and reflected on the columella, 
and placed obliquely to the axis of the shell; edge generally 
short, and dentated or crenulated; as the animal increases in 
dimensions, that part of the columellar lip is absorbed, which 
makes it appear as having no columella; operculum testaceous, 
semicircular, closing the aperture entirely, covered with a horny 
epidermis, and provided internally at the lower end with a tooth- 
like appendage, which fits into a hollow between the prominence 
and lip. 
1. NeERITINA FLUVIATILIS, pl. XVIII, f. 1, 2, 3, and pl. 
XIII, f. 4, 5.—First Ed., pl. 43, f. 1, 2, 3. 
Neritina fluviatilis, Turton, Man., p. 13, f.124; Alder, Mag. 
Zool. and Bot., Il, p. 117; Thompson, Ann. and Mag. Nat. 
Hist., VI, p. 163; Lamarck, An. San. Vert., VI, pt. 2nd, p. 1885 
Fleming, Brit. An., p. 321; Nerita fluviatilis, Mill, Moll. II, 
p 194; Drapernaud, Hist. Moll. p. 31, pl. 1, f. 1; Pfeiffer, I, 
p- 106, f. 37, 38, 39; Fleming, Edin. Ency., VII, p. 82; Ib., 
Brit. An., p. 321; Brard, p. 194, pl. Wnts 9; 105) 2)ssarton; 
Conch. Dic., p. 127; Neritina fontinalis, Brard, Hist. Conch., 
p- 196, pl. 7, f. 115 Theodoxus Lutetianus, De Montford, II, 
p- 351; Da Costa, Brit. Conch., p. 48, pl. 3, f. 8; Pennant, 
Brit. Zool., IV, p. 141, pl. 88, f. 142; Donovan, Brit. Sh., I, 
pl. 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 volu- 
tions, and terminating in a minutely small, slightly produced 
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 epider- 
mis, beneath which the surface is glossy and smooth, but longi- 
tudinal, minute wrinkles, are observable by the aid of a strong 
lens; beautifully streaked, spotted, or mottled, with white and 
purplish-brown, deep umber, or pale brown, and in some in- 
stances 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, Shannon, 
and Bresna in Ireland; and the Forth, Tay, and Clyde in 
Scotland. 
[ TRACHELIPODA 
Famity VII.—PERIsToMIDA. 
Shell conoid, or subdiscoid, with the margins of the aperture 
united; aperture protected by an operculum; fluviatile, and the 
animal haying the power of respiring in water. 
Genus 34.—PaLup1InA.—Lamarck. 
Shell ovate, or oblong; spire somewhat turreted; the volu- 
tions smooth, rounded, and subcarinated; aperture subrotund, 
ovate, or oblong, a little angulated above, slightly modified on 
the inner side by the gibbosity of the body volution; lips united 
all round, with acute edges; operculum corneus, with concentric 
lines of growth, and provided with a sublateral nucleus. 
1. Patupina vivipaRA, pl. XIV, f. 71, 72.—First Ed., pl. 
41, f. 71, 72 
Paludina vivipara, Lamarck, An. San. Vert., VI, pt. 2nd, p. 
173; Brard, Coq. de Paris, p. 174, pl. 7, f. 1; Fleming, Brit. 
An., p. 315; Alder, Mag. Zool. and Bot., II, p. 116; Thomp- 
son, Ann, and Mag. Nat. Hist., p. 17; Cyclostoma viviparum, 
Drapernaud, Hist. Nat. des Moll., p. 34, pl. 1, f. 16, 173; Tur- 
ton, Man., p. 113, f. 118; Brard, Coq. de Paris, p. 174, pl. 7, 
f. 1; Rossmassler, f. 66; Helia vivipara, Montagu, Test. Brit., 
p- 386; Brown, Wernerian Mem., II, p. 527; Viviparus fluvio- 
rum, De Montford, II, p. 247; Paludina achatina, Sowerby, 
Gen., f. 1. 
Shell thin, subconic, oblong-ovate; spire consisting of five 
extremely ventricose, abruptly diminishing yolutions, separated 
by a deep suture, and terminating in an acute apex; aperture 
suborbicular, a little contracted above; pillar lip slightly reflect- 
ed, behind which is a subumbilicus; inside smooth, bluish-white, 
the external bands shining through; whole shell covered with 
an olive-green shining epidermis, beneath which the shell is 
white, with three spiral, dark brown bands on the body, and two 
‘on the superior volutions, which generally grow fainter as they 
ascend, until they become nearly invisible before reaching the 
apex; surface slightly wrinkled longitudinally, several of which 
are coarser than the others, marking the periodical growth of 
the shell; aperture protected by a thin horny operculum. 
In the young condition the shell is subglobose, subpellucid, 
with the bands rather obscure, and the volutions appear more 
flattened above than in the adult state. 
Found in the Thames and other slow rivers, and sometimes 
in ponds. Plentiful in a ditch near Southport, Lancashire. 
Occurs in a stream at Newtownards, County of Down, Ireland. 
2. Pa.upINA AcHATINA, pl. XIV, f. 68, 69.—First Ed., pl. 
41, f. 68, 69. 
Paludina achatina, Lamarck, An. San. Vert., VI, pt. 2nd, p. 
174; Ency. Meth., pl. 458, f. 1, a, b; Rossmassler, p. 109, f. 
66*; Turton, Man., p. 133, f.119; Lymnea vivipara, Fleming, 
Brit. An., p. 3153 Cyclostoma achatina, Drapernaud, p. 36, pl. 
Veta Ss 
Shell thin, oblong-ovate, ventricose ; spire consisting of four 
or five considerably inflated yolutions, separated by a well de- 
fined, deep suture, and terminating in a rather obtuse apex ; 
aperture suborbicular, slightly contracted above, white within, 
with the external bands apparent; pillar lip a little reflected on 
the columella; outer lip thin, and sharp’ on the edge; whole 
shell covered with an olivaceous epidermis, beneath which it is 
provided with three, dark reddish brown, spiral girdles on the 
