Hydatina zonata
(Solander in Lightfoot, 1786)

Order: CEPHALASPIDEA
Superfamily: ACTEONOIDEA
Family: Hydatinidae

DISTRIBUTION

Tropical Indo-West Pacific

PHOTO

Sokodo, Hachijo Island, Japan, 8m, 50mm & 30mm long. 1 July, 2001. Photo: Nishina Masayoshi.

Shell identical in shape to that of Hydatina physis. In H. zonata the colour pattern consists of thin, rather irregular brown lines running across the translucent white shell, essentially parallel to the outer lip of the shell. There are spiral bands around the base and apex of the shell where the brown lines are absent, and sometimes another spiral band simewhere between the base and the apex. These colourless bands are sometimes bordered with a thin brown line. Like H. physis, the animal varies in colour from translucent white with an opaque white margin, as illustrated here, to a deep brownish pink. Anatomically it is identical to H. physis.

Major synonyms include Bulla circulata Martyn, Bulla velum Gmelin, Hydatina vexillum Sowerby.

Reference:
• Lightfoot, J., (1786). A Catalogue of the Portland Museum lately the property of the Dowager Duchess of Portland, Deceased: which will be sold by Auction. 194pp, Plate 1. London.

Authorship details
Rudman, W.B., 2001 (August 8) Hydatina zonata (Solander in Lightfoot, 1786). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/hydazona

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