Planorbis spinorbis. The Round-spired Coil-shell.—In clear springs and springy ditches. Less abundant than the last.
Planorbis contortus. The Twisted Coil-shell.—In the ditches of all the Sussex rivers, and occasionally in very weedy ponds.
Planorbis fontanus. The Shining Coil-shell.—Sparingly in clear water, at Cowfold and Henfield, amongst Callitriche verna (B), and in the Mill-stream at Ratham (J).
Planorbis nitidus. The Streaked Coil- shell.—In a ditch near the ruins of the Priory at Lewes, and in a pond at Old Deane Farm, Henfield.—B. Mr. Unwin has met with it in a ditch in Kingston brooks, near Lewes, adhering to Confervæ. He has found it a good plan to drag out a quantity of the Confervæ, and on reaching home to place it in a basin and pour warm water upon it. The animals at once relinquish their hold and fall to the bottom, when they may be easily collected. Mr. Boner, in a recent letter, has pointed out that Segmentina lineata, Fleming, of Mr. Unwin's list is referable to the present species, Planorbis nitidus Müller, and not to Acme lineata, Draparnaud, as stated ante p. 126. It would seem, therefore, that Mr. Unwin has given the same species twice under different names. Mr. Weaver has seen specimens of this shell said to have been collected in the parish of Harting, but has not found it there himself.
Physa fontinalis. The Stream Bubble-shell.—May be found in water-cress and other aquatic plants in streams and canals, and is everywhere tolerably common. It occurs in most of the ditches of the before-mentioned levels.
Physa hypnorum. The Slender Bubble-shell.—Is rather more local, affecting ponds, ditches, and rank grass in dried-up pools. Mr. W. Jeffery has noted it at Ratham, near Chichester, and at Lindfield. Both these species are gregarious, and may be recognized at once by the polished appearance of their shells, the surface of which, being more or less enveloped by an expansion of the mantle, is kept bright by the lubricating friction which it undergoes. The characters by which fontinalis may be distinguished from hypnorum are the oval instead of oblong shell, larger and wider month, smaller number of whorls (that is, four or five, instead of six or seven), shorter spire, and deeper suture. The foot of the animal in fontinalis is rounded in front instead of lanceolate, and the body is of a uniform greyish colour, instead of being minutely speckled as in hypnorum. Gray considered these two generically distinct,
