Diagnostic characters
Shell solid, tall, slender, spire not noticeably cyrtoconoid; whorls with costae and spiral ridges raised into blunt tubercles where they cross; base with spiral ridges only. Aperture small, with notch at base of columella. Commonly a varix on each whorl. Flesh brownish.
Other characters
The shell has usually 10-12 whorls, but up to fifteen may occur; they are a little swollen and the sutures are rather deep. The last whorl has nine or ten spiral ridges, whorls near the base of the spire have four, the number decreasing towards the apex. On the last whorl there are 12-20 costae and the whorls of the spire bear 11-12. A conspicuous feature of the ornament is the tubercles where costae and ridges cross. The umbilicus is closed. Fawn or light brown; apex, tubercles and columella pale. Up to 8mm high, 3 mm broad; last whorl occupies 40-45% of shell height, aperture 25%.
There is an elongated snout with long slender tentacles at its base, an eye alongside each. Males are aphallic, and the genital duct is open in both sexes. The foot is long and narrow, truncated anteriorly, bluntly pointed behind. The opercular lobe projects backwards from under the operculum as a median ridge. The flesh is fawn-brown with speckles and streaks of black and white; the tentacles may be orange or reddish.
B. reticulatum is found on soft bottoms where Zostera and some other weeds grow, occasionally on stones, or in crevices; it prefers quiet places, It occurs from near L.W.S.T. to depths of 250 m, commoner sublittorally than intertidaliy. It is a detritivore. In the British Isles it is found everywhere except in the North Sea. Elsewhere it ranges from the Black Sea to northern Norway.
The animals are summer breeders. Spawn is attached to shells, stones or weeds and forms a cylindrical ribbon of about 3 mm diameter which is coiled in a tight spiral of 2-4 turns. Its total length is about 25 mm. In all, the spawn contains about 1000 eggs which develop rather rapidly to veliger larvae which are readily identifiable by the square tongue-shaped projection on the outer lip of their shell.