of the District around Colchester.
91
V. cristata, Mull.—I find this species is more frequently
an inhabitant of ponds than V. piscinalis. It occurs every-
where throughout the district, and is one of the shells chosen
frequently by a Caddis-worm to form its ease.
Liminaeidae.
Planorbis lineatus, Walker.—I have seen shells said to
have been found in the Stour within my boundaries, hut
have never taken the species myself.
P. nitidus, Mull.—Occurs in many parts of the district
both in slow streams and ponds, but it is not frequent.
P. nautileus, Linn.—No doubt is frequently passed over
from its small size. I find it sometimes very abundantly in
ponds at West Bergholt. Var. cristata occurs in the same
spots, and is, I think, one of our most beautiful shells.
P. albus, Mull.—Abundant where it occurs, but occasionally
for years it seems almost to die out in some ponds. It is
found on all soils: also in brackish water on the marshes
near Wyvenhoe Park.
P. spirorbis, Mull.—Very abundant. I have found several
distorted specimens in which the whorls are more or less
separated or displaced.
P. vortex, Linn.—Not quite so abundant as the last
species, but found all over the district.
Var. compressa.—Occasionally in the marshes of the Colne.
P. carinatus, Mull.—I find this snail more frequently in
the marshes by the rivers and brooks than in stagnant
ponds. It is said never to be plentiful, but I once found a
shallow pond near Ardleigh Crown swarming with it.
P. complanatus, Linn.—Common throughout the district.
P. corneus, Linn.—I never find this mollusk in ponds
unless they are in the marshes and connected with the
rivers ; there they are fairly plentiful. The largest speci-
mens I have seen were reared in a soft-water butt, at
Wormingford.
P. contortus, Linn.—Common in our rivers and ponds of
stagnant water in many parts of the district.
Physa hypnorum, Linn.—Very local and rare. An occasional