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Brookula crebresculpta (Tate, 1899)

Description: Shell minute, height to width ratio fairly constant in range 1.0 - 1.1. Protoconch smooth, elevated. Teleoconch up to 2¾ whorls, suture deep. Sculpture variable; axial sculpture of moderate strength ribs throughout, at least 20 on last whorl, fading out below periphery or continuing into umbilicus. Fine spiral threads between axials, varying from obsolete to moderate in strength, often stronger on base. Umbilicus open, varying from narrow to wide. Aperture circular, margin entire, not thickened. Shell colourless transparent when fresh, becoming opaque with age.

Size: Up to 1.1 mm in length.

Distribution: Endemic to Australia: Fraser Island, Queensland, southwards to SA, including Tasmania.

Habitat: A few records are from beach washup, but most are from 5-1200 m. Moderately common.

Comparison: See B. angeli.

Synonymy: Brookula turbinata Laseron, 1954 falls within the range of variation (NEW SYNONYM).

Remarks: This is not a well-defined taxon, and I would not be surprised if later study showed more than one species was grouped here. The number and strength of axial ribs is variable, and they may fade out on the periphery of the last whorl or continue into the umbilicus. The extent to which the umbilicus is open is also variable.

Figs. 1, 2: Off Broken Bay, NSW, in 145 m (C.462818) (Photo Sue Lindsay, Australian Museum)