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PINNA LEVIS.

SMOOTH PINNA, OR HÀM SHELL.

GENERIC CHARACTER.

Animal Limax. Shell sub-bivalve, fragile, erect, gaping at one end, and furnished with a byssus or beard: hinge toothless, and uniting the valves into one.

SPECIFIC CHARACTER.

Shell nearly triangular, horn-colour, smooth: valves rugose on the posterior part,

PINNA LEVIS testa sub-triangulari cornea lævi: valvis posterius

rugosis.

This species of Pinna which differs from any that has been before described as a British shell; and if we are not mistaken, from either of the Linnæan or Gmelinian species of the genus also; was received by A. M'Leay, Esq. among other curious shells that were dredged up on the coast of Shetland.

The difference between this and the other analogous kinds, seems to consist in its being of a more triangular form, and in not having

the least trace of spines or murication: from the beak descend some very obsolete longitudinal striæ, but the surface is in general perfectly smooth and glossy, notwithstanding the specimen before us has at first sight a rugged aspect; the shell having been greatly bruised or mutilated in its growth, and afterwards uncouthly repaired by the animal inhabitant.