Pisidium nitidum. The Glossy Pea-shell.—In ditches at Henfield, Lewes and Eastbourne.—B.
Fam. Unionidæ.
Unio pictorum. The Painter's Mussel.—Generally distributed in ponds and streams. Common in the Cut near Lewes, and in the Ouse occasionally; varying very much in appearance, specimens in the Ouse being much darker, and having an extraneous coat, evidently from some matter with which the water is impregnated.—U. Mr. W. Jeffery reports its occurrence at Burton, near Petworth. It is somewhat singular that none of the Sussex lists include the allied species, Unio tumidus, which is very generally distributed throughout the country, and sometimes occurs in company with pictorum. In the parish of Hailing neither of these two species has been met with.
Anodonta cygnea. The Swan Mussel.—Common in ponds and pools, in the mud of which it may be found deeply sunk, with the posterior end only of the shell, where the respiratory syphon is situated, above the surface. Some unusally large specimens of this mussel have been taken out of the Vicarage Pond at Cowfold, near Horsham. One of these, now before me, measures seven inches by three inches and a half. This is much above the average size; but some years ago several were taken out of a decoy pond in Firle Park, Sussex, measuring eight inches in length and nine in circumference.[1]
It would be proper to introduce here the family Dreissenidæ, in order to notice the Zebra Mussel, Dreissena polymorpha, which is generally distributed in our navigable rivers; but none of the Sussex conchologists make mention of it in their lists, and for the present therefore it remains excluded from the freshwater Mollusca of that county.
UNIVALVES (GASTEROPODA).
Order Pectinibranchiata.[2]
Fam. Neritidæ.
Neritina fluviatilis. The River Neritina.[3]—Usually found on a stony or gravelly bed in slow rivers, streams and lakes, into
