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(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).

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

Colour:
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.

Animal:
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.

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

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

Tectura testudinalis