Tectura testudinalis

(Müller, O.F., 1776)

Description (shell):
Shell conical, apex toward anterior margin with anteriorly projecting beak (more discernible in young shells). Profile more variable than in Acmaea virginea , often showing a marked apical inflection in both posterior profile (mainly convex) and anterior profile (mainly straight). Sculpture as in Acmaea virginea (T. testudinalis-drawing).

Up to 30 x 24 x 10 mm, commonly 14 x 10 x 4 mm in littoral habitats.

Shell with light background overlain by series of' irregularly branched brown bands radiating from apex to produce a tessellate pattern. Inside white with outside pattern visible marginally; apical region chocolate brown.

The white animals have a large head with a pair of long tentacles and a pair of eyes at their base. Outer lips on snout with narrow, somewhat stiff, outer fringe; incomplete ventrally where a broad, lobed region bounds mouth. Mantle edge cuprous green with two staggered rows of short tentacles. The foot is oval and broad.

On boulders and small, smooth stones, particularly those encrusted with red algae such as Lithothamnion ; from LWNT to 50 m.

A circumpolar species, not in the southern North Sea (Distr. T. testudinalis).