Physa. In and near fresh-water.
12. P. hypnorum, Linn. (Bulla.)—Helix, Physa, Limnæa, and Aplexa turrita and marmorata. Pools and lakes, Brit. generally, C.
13. P. fontinalis, Linn. (Bulla.)—Turbo, Planorbis, Bulimus, and Ph. adversus, bulla, bulloides, and fluviatilis.—Brit. pools, lakes, and ditches, C.
Ancylus. In fresh-water.
14, 15. A. fluviatilis, Müller.—Patella lacustris.—Running streams, on stones and plants generally, C. Oval, apex turned to left.
16, 17. A. oblongus, Lightfoot, (Patella.)—A. and P. lacustris. More lacustrine than No. 14, Mc. Oblong, apex turned to right.
Planorbis. In fresh-water.
18. P. corneus, Linn. (Helix.)—P. and H. cornu-arietis, purpureus, and similis, P. nana (young).—Ponds and ditches generally, C.
19. P. albus, Müller.—Helix and P. hispidus, hirsutus.—Distribution general, C. Finely ciliated in lines.
20. P. glaber, Jeffreys.—P. lævis, Alder.—Penzance, Falmouth, Swansea, Belfast, etc., Mr.