About Testudinalia testudinalis (O.F.Müller, 1776)
Testudinalia testudinalis (O.F.Müller, 1776) has a low domed, oval-shaped shell. Its maximum size reaches 30 mm in length, 24 mm in width, and 10 mm in height, but most individuals grow to approximately half of this maximum size. The shell's apex is positioned toward the anterior end, and fine ridges radiate outward from the apex. The shell has distinct brown and white banding. The mantle, the body wall located directly beneath the shell, curls along its edges to form a collar. This species has a broad, oval foot, and its head carries two sensory tentacles, each with a tiny black eye at its base. Testudinalia testudinalis is distributed across northern regions of the Pacific Ocean, the Northwest Atlantic Ocean, and European waters. It inhabits the neritic zone, ranging from the low water mark down to around 50 meters in depth. It most commonly occurs on stones and boulders, particularly those that are encrusted with red crustose algae such as Lithothamnion.
