Lymnaea. 
MOLLUSCA. 
97 
1. Lymnaea pyramidalis. —The Pyramidal Lymnaea, pi. 
XLVI. fig. 1, 2. 
Lymncea pyramidalis. Brard; Ann. du Mus. XV. pi. 24, 
fig. 1, 2. Deshayes, II. p. 95, pi. 10, fig. 14, 15. Sowerby, 
VI. p. 53, pi. 528, fig. 3. Fleming, p. 270. Brown, Elements 
Fossil Conchology, p. 59, pi. 4, fig. 13. 
Elongated, subcylindrical; body large; spire pyramidal, small, 
with five inflated, well defined volutions, the apicial one acute; 
aperture oblong, half the length of the shell, a little contracted 
above, and rounded below; outer lip sharp on the edge, and 
but slightly expanded; callus on the columella, with a shallow, 
faintly defined furrow in its centre. 
Fresh Water formation, Headon Hill, Isle of Wight. 
2. I/ymn;ea maxima. —The Great Lymnaea, pi. XLVI. 
fig. 3, 4. 
Lymncea maxima. Sowerby, VI. p. .53, pi. 528, fig. 1,1. 
Fleming, p. 276. 
Oblong-ovate, subcylindrical; body large, and slightly inflated; 
spire a little pyramidal, with five moderately convex volutions, 
terminating in an obtuse apex; aperture oblong, a little con¬ 
tracted above, .and rounded below, occupying about half the 
length of the shell; outer lip thin; columellar lip but slightly 
reflected. 
Fresh Water formation, Isle of Wight. 
3. Lymnaea minima. —The Least Lymnaea, pi. XLVI. fig. 
5, 6, 7. 
Lymncea minima. Sowerby, II. p. 156, pi. 169, fig. L 
Fleming, p. 276. 
Oblong-oval, convex, smooth; body large; spire small, with 
four rather inflated volutions, terminating in an acute apex; 
aperture elongated, contracted and pointed above, and slightly 
straitened below, occupying half the length of the shell. Length 
a little more than a quarter of an inch. 
Fresh Water formation, Isle of Wight. 
4. Lymn/EA longiscata. —The Lengthened Lymnaea, pi. 
XLVI. fig. 8, 9. 
Lymncea longiscata. Sowerby, IV. p. 57, pi. 343. Fleming, 
p. 276. Lirnneus longiscatus? Brongniart, Mem.sur des Terr, 
p. 16, pi. 1, fig. 9* Ann. du Mus. XV. pi. 22, fig. 9. 
Elongated, smooth, shining, with regular lines of growth; 
body large; spire of medium length, with six or seven broad, 
oblique, slightly inflated volutions, ending in an acute apex; 
aperture ovate, elongated, occupying two-fifths the length of 
the shell, contracted and acute above, and rounded below; outer 
lip thin-edged; pillar lip broad, obtuse at the edge, with a shal¬ 
low twisted plait. 
Upper Fresh Water formation, Headon Hill, Isle of Wight. 
5. Lymnjea fusiformis. —The Spindle-shaped Lymnam, 
pi. XLVI. fig. 10, 11. 
Lymncea fusiformis. Sowerby, II. p. 155, pi. 169, fig. 23. 
Fleming, p. 276. 
Subfusiform, smooth, and shining; body large, slightly inflated; 
spire small, pyramidal, with five rather flat-sided volutions, the 
apicial one acute; aperture elongated, narrow, slightly contracted 
above, and rather rounded below, occupying about half the 
length of the shell; entire surface coverod with rather sharp, 
regular lines of growth. 
Fresh Water formation, Isle of Wight. 
6. Lymnjea columellaris _The Columellar Lymnaea, 
pi. XLVI. fig. 16, 17. 
Lymncea columellaris. Sowerby, VI. p. 53, pi. 528, fig. 2. 
Oblong-ovate, smooth; body very large; spire short, with 
four inflated volutions; aperture oblong, wide, occupying about 
half the length of the shell, contracted above, much expanded 
and rounded below; outer lip thin, ample; inner lip with a 
broad, greatly twisted, thick columella. 
The shortness of the spire will readily distinguish this from its fossil 
congeners. 
Fresh Water strata, Hordwell Cliff. 
Genus LII.—PLANORBIS— Muller. 
Shell discoidal, umbilicate; spire and base depressed; 
apex always distinct; the volutions turning nearly on the 
same plane, from right to left, so that when the spire is 
held upwards, and the aperture next the observer, it is 
situate on the left hand side; volutions ventricose, in 
many species, often carinated, either above or below; 
aperture entire, obliquely semilunate, its length and 
breadth being nearly equal, but broader than long in 
some instances; outer lip sometimes thickened; umbili¬ 
cus very wide; destitute of an operculum. 
1. Planorbis obtusus -The Obtuse Planorbis, pi. 
XLVI. fig. 12, 13. 
Planorbis obtusus. Sowerby, II. p. 91, pi. 140, fig. 3. 
Fleming, p. 279. 
Depressed, discoidal, smooth, pellucid, and shining; volutions 
few, greatly concealed, embracing; aperture oblique, obtuse, 
subcordiform. 
Fresh Water formation, Isle of Wight. 
2. Planorbis hemestoma. —The Red-mouthed Planorbis, 
pi. XLVI. fig. 18, 19, 20. 
Planorbis hemestoma. Sowerby, II. p. 91, pi. 140, fig. 6. 
Fleming, p. 279. 
Discoidal, depressed, smooth; volutions partly concealed ; 
spire convex, umbilicate ; base flat; aperture subtriangular, ob¬ 
lique. Diameter one line; thickness the fourth of a line. 
Plastic Clay, Plumstead. 
3. Planorbis cylindricus —The Cylindrical Planorbis, 
pi. XLVI. fig. 21, 22. 
Lymncea cylindricus. Sowerby, II. p. 90, pi. 140, fig. 2. 
Fleming, p. 279. 
Cylindrical; three or four adpressed volutions, with concen¬ 
tric, and obscurely elevated, striae on the left side; aperture 
transverse, oblong, quadrangular, the angles obtuse, its width 
exceeding its length, but without any indentation from the 
second volution. Diameter nearly three times its thickness. 
Fresh Water formation, Isle of Wight. 
4. Planorbis Lens —The Lens-shaped Planorbis, pi. 
XLVI. fig. 26, 27. 
Planorbis Lens. Sowerby, II. p. 91, pi. 140, fig. 4. Fle¬ 
ming, p. 279. 
Lenticular, flat, equally concave above and below, subcari- 
nated, with embracing volutions; aperture subcordate, and very 
oblique. Thickness about equal to a sixth of its diameter. 
Fresh Water formation, Isle of Wight. 
