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HAMINOEIDAE |
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Cylichnatys campanula Burn, 1978 Description: Shell thin, elongate, involute, width about 50% of shell length. Apex slightly sunken, not umbilicate. Last whorl with sides parallel or weakly constricted over middle part of shell. Aperture narrow over top half, wide at bottom; outer edge sharp. Columella smooth, curved, parietal wall with thin callus. Whole surface smooth or with coarse axial growth lines, and sometimes widely-spaced spiral groves. Shell translucent when fresh, becoming opaque white with age. Size: Up to 4 mm in length. Distribution: Endemic to Australia: Port Stephens, NSW, southwards and around southern Australia to the Swan River estuary, southwestern WA. Habitat: Lives in the intertidal and down to 18 m in estuaries, in seagrass and on mud. Common. Comparison: This is like Retusa atkinsoni, but has no apical umbilicus. Remarks: Burn (1978) gave a description of the genus Cylichnatys and of his new species in which he stressed that the spiral sculpture was a prominent character. But only a small proportion of the NSW specimens I have examined show such spiral sculpture. Perhaps it is prominent in live taken specimens, but in dead shells it is not apparent, even in specimens which do not appear to be worn. Burn (1978) gave the variation in shell width as 30-60% of shell height, but the variation is not as large in NSW specimens. For the shells in Fig. 1 the ratio is 50%, which is typical of NSW specimens. Fig. 1: a. and b. Cronulla Beach, Sydney, NSW (C.395014). Fig. 2: Apex of Fig. 1 specimen a (C395014). |
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