Diagnostic characters
Shell rather glossy, semitransparent under a thin periostracum; spire well-developed, whorls moderately swollen, the last one large. Umbilicus absent. Aperture oval, pointed adapically. Operculum with concentric rings, partly calcified.
Other characters
The apex is pointed and the apical angle is 55-60°. There are 5-6 whorls. The outer lip is a little turned out, especially basally, and the inner lip is concave where it rests against the last whorl. Though there is no open umbili¬cus a slight groove lies alongside the columellar lip. The shell is horn-coloured though nearly white if the periostracum is lost. Up to 10 mm high, 6mm broad; last whorl occupies about three quarters of the shell height, the aperture about 60%.
The head bears a long snout with a bifid tip. The cephalic tentacles are long, each with a basal eye. Males have a double-tipped penis recurved into the mantle cavity. All animals have a ciliated groove on the floor of the mantle cavity, its right edge expanding anteriorly to form an exhalant siphon. The foot is broad anteriorly with recurved lateral points. The flesh is grey with yellow speckles.
B. tentaculata is common in hard water areas of the British Isles (absent from Cornwall, Devon, North Wales and northern Scotland), especially in the gentler reaches of rivers, where it creeps over the vegetation or on the bottom, feeding primarily on epiphytic growths but also filtering suspended particles (Schafer, 1952, 1953a,b; Tsikhon-Likanina, 1961; Meier-Brook & Kim, 1977). The species is generally spread throughout the western Palae-arctic region.
Breeding occurs late spring to early summer (Lilly, 1953). Egg capsules are fastened to the underside of leaves, side by side, to form 2-4 rows with 10-20 capsules in all (Nekrassow, 1929). There is a single reddish egg in each capsule which hatches to a small snail in 2-3 weeks.