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Adamnestia arachis (Quoy & Gaimard, 1833)

Description: Shell thick, elongate, involute, width about 38% of shell length. Apex with narrow umbilicus. Last whorl with sides weakly convex over whole length of shell. Aperture narrow over top 2/3 of shell, wide at bottom; outer lip sharp. Columella smooth, with narrow callus reflected outwards; parietal wall with thin white callus overlaying periostracum, often peeled away. Whole surface with dense microscopic spiral grooves, weaker or absent in middle. Shell texture almost chalky; colour white or pale fawn with thin or thick brown periostracum, worn away on most specimens.

Size: Up to 25 mm in length, most commonly 10-15 mm.

Distribution: Southern Qld, southwards and around southern Australia to southwestern WA, including Tas.

Habitat: Empty shells are from beach washup and dredgings down to 182 m. Living specimens are known from soft sediments in estuaries intertidally, but no doubt have a wider bathymetric range. Common.

Comparison: This species is similar to Cylichna thetidis, for which the comparison is given below. Retusa atkinsoni and Retusa iredaleana are also similar, but neither of these exceed 6 mm in length.

Synonymy: Adamnestia peroniana Iredale, 1936 is a previously recognised synonym.

Figs. 1, 2: Off Chinamans Beach, Middle Harbour, NSW, in 11 m. (C.394986).


Copyright Des Beechey 2018