Fossarina patula Adams & Angas, 1863
Description: Shell low, width about equal to height, aperture two-thirds of total height. Whorls rounded, sculptured with about five low, broad spiral ribs. Base rounded, more weakly ribbed than body whorl. Aperture large, outer lip simple; columella and aperture smooth. Umbilicus open, closed to variable degree by columella callus. Shell usually eroded; exterior colour white or brown. Interior white to grey, slightly nacreous.
Size: Up to 5 mm high, 5 mm wide.
Distribution: Endemic to Australia; Newcastle, NSW, to eastern Vic.
Habitat; Lives around the middle of the intertidal zone on rocky shores, sheltering in crevices and among barnacles.
Synonym: Fossarina brazieri Angas, 1871
Remarks: Fossarina legrandi Petterd, 1879 is a species of similar size and shape, known from Twofold Bay, NSW, to south-western WA. It is distinguished from F. patula by lacking the spiral ribs, having a smooth surface boldly marked with black or brown and white, and sometimes having an golden iridescent sheen.
Figs. 1,2: Middle Harbour, NSW (C.006482)