WITH A LIST OF SPECIES OBSERVED.
229
Order PULMONOBRANCHIATA.
Family LIMNAEIDAE.
Planorbis nautileus, L. Local; abundant between Green-
hithe and Darenth Creek; also few associated with Hydrobia
jenkinsi, Plumstead Marshes.
P. spirobis, Mull. Common ; and generally distributed.
P. vortex, L. Somewhat more local; Tilbury Marsh.
P. carinatus, Mull. Local; near Abbey Wood.
P. complanatus, L. Common upon the Marshes both sides
of the river.
P. corneus, L. Local. Specimens from the Marshes are not
generally so fine as those inhabiting the adjacent ponds and ditches.
P. contortus, L. Very local ; few from ditch, West Tilbury
Marsh.
Physa hypnorum, L. A few shells in ditch upon Plumstead
Marshes.
P fontinalis, Linn. Common ; and widely distributed.
Var. inflata, Moq. Marsh near Abbey Wood Station.
Var. oblonga, Jeff. One specimen ; ditto, ditto.
Limnaea peregra, Mull. The commonest fresh water shell
upon the Marshes.
Var. ovata, Drap. Near Abbey Wood Station.
Var. acuminata, Jeff. Ditto, ditto.
Var. labiosa, Jeff. Few specimens ; Plumstead Marshes.
Var. scalariforme, Jeff. Two shells only at Abbey Wood.
L. stagnalis, L. Local ; a few at Purfleet; also in pond
Shooter's Hill.
Var. albida, Jeff. One shell; Coldharbour Marshes, near
Purfleet.
L. palustris, Mull. Common; everywhere.
L. truncatula, Mull. Scarce and local; Plumstead and Erith
Marshes.
Order PULMONIFERA.
Family ARIONIDAE.
At present I have recorded six species only of slugs from the
Marshes and immediate neighbourhood.
Arion ater, L. (Black Slug.) Plumstead Marshes. One
specimen kept in captivity attained the length of 81/2 inches when