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Pusillina (Haurakia) angulata (Hedley, 1907)

Description: Shell lightweight, moderately short and wide, spire almost straight-sided. Protoconch of 1 smooth whorls, with distinct junction to teleoconch. Teleoconch up to 3 evenly rounded whorls. Spire whorls usually smooth, occasionally with weak, irregular folds. Last whorl weakly or strongly angled at periphery, sometimes with spiral cord on angulation; whorl becoming rounded and cord fading out towards aperture of adult shells. Aperture wide, anterior edge formed into broad, shallow excavation, posterior sinus broad; outer lip expanded, with varix externally. Umbilicus present as narrow slit in some mature shells. Shell colourless transparent when fresh, becoming opaque white with age.

Size: Up to 3.5 mm in length.

Distribution: Endemic to Australia. Australian Museum specimens: Fraser Island, Queensland, southwards and around southern Australia, to central Great Australian Bight, including Tasmania.

Habitat: On the continental shelf, 37-384 m.

Comparison: This species is recognised by the overall smooth and glossy surface with a single spiral cord on the periphery of the last whorl.

Synomymy: None.

Remarks: The angulation and spiral rib on the last whorl fade out as the shell reaches maturity, being more pronounced in immature specimens in which the varix has not started to form.

Fig. 1: Off Sydney, in 200 m (C.396066)

Fig. 2: 6 km east of Minstral Point, Sydney, in 61 m (C.396060)

Fig. 3: Original figure from Hedley (1907)

 

Copyright Des Beechey 2010