Appearance
''T. testudinalis'' has a low domed shell, oval in outline. It can grow to up to 30 x 24 x 10 mm but typically is about half this size. The apex is towards the anterior of the shell and fine ridges radiate from it. The shell is banded with brown and white. The mantle is the part of the body wall immediately under the shell and at the edges it is curled round to form a collar. The foot is broad and oval. The head bears two sensory tentacles with a tiny black eye at the base of each.
Distribution
''T. testudinalis'' occurs in northern regions of both the Pacific and Northwest Atlantic Oceans and in European waters. It is found in the neritic zone from low water mark down to a depth of about fifty metres. It is usually found on stones and boulders, especially those encrusted with red crustose algae such as ''Lithothamnion''.
Behavior
Red eggs are laid in a sheet in the spring and the larvae are planktonic.
Habitat
''T. testudinalis'' occurs in northern regions of both the Pacific and Northwest Atlantic Oceans and in European waters. It is found in the neritic zone from low water mark down to a depth of about fifty metres. It is usually found on stones and boulders, especially those encrusted with red crustose algae such as ''Lithothamnion''.References:
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