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Agnewia tritoniformis (Blainville, 1832)

Description: Shell with rounded whorls, with about 11 broad, low axial ribs, crossed by about 40 fine, smooth, spiral riblets, which group together to form 6 or 7 larger spiral ribs, well defined on the posterior of the body whorl, but more diffuse on the anterior. Axial and spiral ribs fawn, the interspaces black, giving a fenestrate appearance. Columella smooth, outer lip toothed in mature shells, interior white, lip sometimes yellow. Operculum corneous.

Size: Average length 20 mm, maximum 35 mm.

Distribution: Australia and northern New Zealand; in Australia, Caloundra, Qld, to Yorke Peninsula, SA, including Tas.

Habitat: Under rocks and in pools on the open coast. Common in NSW.

Remarks: Fig. 3 shows a section of the egg mass of this species, deposited on a piece of shell.  The egg mass consists of a hundred or so hemispherical, transparent capsules of about 3 mm in diameter, each of which contains hundreds of  larval shells.  The brown capsules are still filled with larval shells; the colourless capsules have broken open at the top and have emptied.

Figs. 1,2: Minnie Waters, NSW (C.346753)

Fig. 3: Egg mass (C.403738)

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Copyright Des Beechey 2000