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ON A NEW GENUS OF NUDIBRANCHIATA

FAM. ELYSIADEA.

BY THE REV. J. E. TENISON WOODS, F.G.S., F.L.S., Corr. Mem. Roy. Soc. Tas., etc.

The Elysiadae are shelless mollusca with no distinct mantle or respiratory organ, all being performed by the ciliated surface of the body. The stomach is central; the hepatic organ branched, extending almost the whole length of the animal; eyes sessile, and tentacles simple or obsolete.

There are five known genera of the family, viz.:—ELYSIA, with tentacles; ACTAEONIA, leech-like and with tentacles; CENIA leech-like, linear dorsal tentacles; LIMAPONTIA, head truncated and with arched lateral ridges; RHODOPE, worm­like.

To this family I have found an addition of marked and peculiar generic character. This new genus I propose to dedi­cate to Mr. Morton Allport, as a slight mark of appreciation of his great services to science and acclimatization in Tasmania.

ALLPORTIA, Nov. GEN.

Corpus expansum, tenue, antice et postice omnino complanatum, occulis submarginatis.

ALLPORTIA EXPANSA. n.s. Corpus supra olivaceum, pede pallidiore; occulis appoximatis punctis parvis atratis numerosis, compositis; infra lineis ramulosis albis (hepaticis?) conspicuis.

Animal expanded thin, leaf-life, with no distinct foot, eyes anterior; body without tentacles or ridges.

ALLPORTIA EXPANSA. n.s. Animal of a deep olive above, smooth; eyes close together and slightly raised about one fourth of the whole length within the anterior edge. Under the lens the eyes appear to be composed of many minute dots. No other organ visible above. Foot much paler, the hepatic organs appearing as a creamy white branching plume down the median line. Length, 30; breadth, 20 millimetres. Common under stones among the rocks at Southport.

This singular mollusc moves with some rapidity like a pale gelatinous expansion of extreme tenuity. Though without shell or apparent muscles, it has such contractile power that it can move itself in any direction and raise itself nearly erect. While the highly organised testaceous mollusca can move only with difficulty, this delicate creature can recover its position at once easily, even when placed on its back. It is of such extreme tenuity, however, that on being placed in spirits it becomes opaque, and the details of its structure are lost. Type specimens are preserved for the Museum.