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Austroginella johnstoni (Petterd, 1884)

Diagnosis: Shell medium in size; white to pale yellowish; strongly narrowed anteriorly; spire medium height with shouldered whorls; weak nodule or axial fold on body whorl just before varix; aperture moderately broad; lip smooth, rapidly thickening posteriorly with a well defined posterior notch, bordered by a parietal nodule; external varix present; siphonal notch present; heavy ventral callus; columella with four strong plaits occupying half or more than half of the aperture.

Size: Adults 6-9 mm in length.

Distribution: Australian Museum Collection: Coffs Harbour , NSW, to Portland , Victoria , and Tasmania .  Lives in sand in the low intertidal, and down to 54 metres.  Common, particularly as a beach shell.

Comparison: This species is very similar to A. muscaria, but is smaller; 6-9 mm compared to 10-16 mm for A. muscaria.  The ventral callus is heavier than in A. muscaria, making the whole ventral surface of the shell almost flat in very mature specimens.  The nodule or fold on the outside of the body whorl just before the varix is much weaker in A. johnstoni.  The habitat of the two species is similar. (See Identification of beach specimens)

Remarks: Murray (1959) reported this species living intertidally in sand in Port Phillip Bay , Victoria ; some were on the surface of the sand, but mainly they were found buried at the end of  6-8 inch long tracks.  Murray provides a description and photograph of the animal.  Ponder & Taylor (1992) collected the species live at 2-6 metres depth in Twofold Bay , NSW.  They fed the animals with small bivalves in the laboratory, and found that they drilled holes in the bivalves, apparently by chemical dissolution.  The size of the holes was smaller than the mollusc’s proboscis, so they proposed that the mollusc introduces a toxic secretion through it to kill or relax the prey.

Figs. 1,2: Collaroy Beach, Sydney (323678).