Marstoniopsis scholtzi: Diagnostic characters
Shell small, delicate, semitransparent (but surface usually covered by encrust¬ing deposits). Apex blunt and flattened, whorls tumid and sutures deep. Ornament of growth lines only. Umbilicus distinct. Aperture egg-shaped, with peristome.
Other characters
The shell has 4-5 whorls. Clean shells are a pale horn colour, but their encrus¬tations usually make them dark. Up to 2.5 mm high, 2 mm broad; last whorl occupies 65-70% of shell height, aperture 40-45%.
The animal is like other hydrobiids, with a tapering, bifid snout, long, very contractile tentacles each with a basal eye, but it lacks a pallial tentacle. In males a penis arises behind the right tentacle and curves back into the mantle cavity, ending in a long flagellum. The foot is approximately shield-shaped, pinched a little in the middle, rounded posteriorly. The flesh is grey; a yellow spot lies over each eye.
M. scholtzi is found on plants such as Glyceria and amongst filamentous algae to a depth of 2-3 m in lakes, canals, and rivers throughout central and northern Europe, except Scandinavia. In the British Isles, however, it is limited to a few canal sites in Cheshire, around Manchester.
Breeding occurs May-July (Jackson & Taylor, 1904) or perhaps for longer (Dussart, 1977). Egg capsules are attached singly to the surface of the plants on which the snails live. Each is more or less hemispherical, fastened by the flat base and with a keel across its summit, and contains one egg, which hatches as a juvenile in about six weeks.