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Sinezona pacifica (Oliver, 1915)

Description: Shell trochiform, width greater than height, spire low. Teleoconch flat above selenizone, with weak spiral ribs and axials from suture that do not reach shoulder. Sculptured below selenizone with strong axial ribs that fade out on base; whole surface from selenizone to base with about 20 fine spiral treads, and a few stronger spirals around umbilicus. Foramen one-sixth of whorl before margin, above periphery, selenizone behind foramen, with moderately raised flanges; length of foramen and selenizone one-half to three-quarters of whorl. Umbilicus open, without bordering rib, forming continuous curve with base. Operculum corneous. Shell colour white.

Size: Up to 1 mm in height.

Distribution: Australia and New Zealand, Lord Howe Is., Norfolk Is., Macquarie Is.; in Australia, from northern NSW to south-western WA.

Habitat: Known from beach specimens, under stones and from algae washings intertidally, and down to about 20 m. Common.

Comparison: See Sukashitrochus atkinsoni.

Remarks: Sinezona beddomei (Petterd, 1884), from Tasmania, is very similar to this species, but is said to lack the spiral threads between selenizone and umbilicus.

Figs. 1,2,3:  Lord Howe Island (C.059763) (SEM Photos Sue Lindsay)


Copyright Des Beechey 2004