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Microdiscula charopa (Tate, 1889)

Description: Shell minute, spire flat or slightly sunken. Protoconch smooth, about 1 whorls, first whorl sloping downwards. Teleoconch of about 3  rounded whorls, smooth apart from fine, dense axial growth ridges. Aperture nearly circular, outer lip simple, thin. Umbilicus widely open. Shell transparent becoming opaque white with age.

Size: Up to 1.3 mm diameter.

Distribution: Endemic to Australia: Port Stephens, NSW, southwards and around southern Australia, to Shark Bay, WA, including Tasmania.

Habitat: Specimens are from intertidal and shallow subtidal rock and algal washings, and from beach washup. Common.

Synonymy: Helisalia pallida Laseron, 1954 is a previously recognised synonym.

Remarks: The anatomy of this species was described in detail by Ponder (1990).

Figs. 13: St Helens Point, Tasmania (C.213600). The dried animal is inside the shell, and the operculum is visible in the aperture.

 

Copyright Des Beechey 2016