Shell conical with apical hole shaped like a figure-of-eight, placed about one third of shell length behind anterior end. Surface with numerous radiating ridges crossed by others which often have an upturned edge and lie parallel to the apertural lip. The anteroposterior axis of the cone is longer than the transverse, and the posterior end broader than the anterior. 20-30 ridges radiate from the apex with smaller ones in furrows between the main ones. The aperture has a crenulated edge and its lip is marked internally by short ridges under the furrows of the outer surface. In side view the lip arches slightly towards the apex. White, with radiating bands of brown or green. Up to 25 mm long. 15 mm broad, 10 mm high.
The animal has a large head and snout with two tentacles at its base, each with a lateral eye stalk; that on the right has a tentacle behind the eye stalk. The mantle edge is thick and elongated to form a curtain over the sides of the foot; it bears warty papillae and others lie in the grooves at the edge of the shell. The mantle edge projects through the apical hole to form a short siphon. The foot is an elongated oval in outline, with 30-35 epipodial tentacles, alternately long and short. White, yellow, orange or red, often with darker speckling.

Keyhole limpets occur on rocky shores from L.W.S.T. to 250 m deep, usually under stones or ledges between tidemarks, on stones or shells sublittorally, feeding on sponges which they mimic in colour. They are not uncommon on most British and Irish coasts except those facing the North Sea. The species ranges from about 60° N to the Mediterranean.

The animals breed December to May (Plymouth). Eggs are passed from the genital opening to the anterior end of the mantle cavity then down the sides of the foot and are fastened to the substratum, usually the underside of a stone, partly by their own adhesive coat, partly by a secretion from glands in the foot. At some stage in this process they must be fertilized.