given by Mr. Gwyn Jeffreys, in his 'British Conchology' (vol. i., pp. 12–15).
Pisidium amnicum. The River Pea-shell.—Formerly the species of this genus were all classed with Sphærium, but, independently of their smaller size, they differ in the shape of their shells, which are not equilateral,—that is, the beak is situated near the shorter end,—and in having but one contractile tube or syphon, instead of two. The name Pisidium was bestowed from the gregarious habits of the species, individuals of which may often be found in considerable quantities, scattered about like peas. Pisidium amnicum is by no means uncommon in rivers and gently running streams, residing wholly at the bottom, and partly buried in the mud. In the parish of Hailing it is widely distributed along the water-courses traversing the Down Park and the Nyewood meadows.—W. In the neighbourhood of Lewes, however, Mr. Unwin considers it somewhat rare, although he has found it iu the Cut, and in the streams which empty themselves into the Ouse. In the vicinity of Brighton, also, it is not considered common.—M.
Pisidium fontinale. The Stream Pea-shell.—Mr. Gwyn Jeffreys has described four varieties of this species, which have been catalogued by some conchologists as specifically distinct, under the names Henslowianum, pulchellum, pallidum and cinereum. Mr. Unwin has entered it in his Lewes list of Mollusca, under the name Henslowianum, and remarks that he has only met with two specimens. In the Brighton list it is included as P. pulchellum and marked "rare." Mr. Weaver has catalogued it, under the name cinereum, as a species inhabiting the streams in the East Halting district. It is reported to occur, also, in the vicinity of Eastbourne.—G.
Pisidium pusillum. The Little Pea-shell.—In ditches in the levels of the Arun and the Adur, and in ponds at Cowfold amongst Lemna minor.—B. Occasionally amongst freshwater Algæ, with other minute species, in the vicinity of Lewes.—U. Under the name obtusale, Mr. Weaver has recorded it as tolerably plentiful in the parish of Halting in a shallow water-course in a meadow known as Pannell's Hole, and Mr. W. Jeffery reports that it is found at Burton, near Petworth. It is recorded with doubt as occurring at Eastbourne (G), and noted as rare in the neighbourhood of Brighton (M).
