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)
Copyright Des Beechey 2000