Stomatella impertusa (Burrow, 1815)
Description: Shell very flat, body whorl expanded, width about 3 times height. Apex at posterior edge of shell. Sculptured with fine spiral grooves visible only under a lens, crossed by irregular growth lines. Exterior colour extremely variable; uniform fawn, grey, green or black, or with stripes, spots or mottling. Interior silvery and iridescent.
Size: Up to about 25 mm.
Distribution: At least Sydney to south-western WA, and possibly more widely distributed.
Habitat: Under stones in rock pools, at and below low tide. Common.
Remarks: S. impertusa is common in Sydney, and extends around southern Australia to at least south-western WA. Shells from northern NSW and Queensland may be the same species or may be a closely related species with Indo-Pacific distribution. The south-western WA shells have been separated as Stomatella auricula (Lamarck, 1816), but they do not show consistent differences to the south-eastern shells, so that name is placed in synonymy. Other probable synonyms of S. impertusa, based on colour variations, are Stomatella nigra Quoy & Gaimard, 1834, Gena strigosa Adams, 1850 and Placomotis illusus Iredale, 1940, from Norfolk Is.
The external anatomy of S. impertusa has been described and figured by Hedley (1917, p. 703).
Figs. 1,2,3: (DLB4941)
Copyright Des Beechey 2000