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RISSOIDAE |
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Rissoina (Rissoina) ferruginea (Hedley, 1904) Description: Shell large for genus, tall and slender, spire almost straight to weakly concave. Protoconch of about 2 whorls, with indistinct junction to teleoconch. Teleoconch up to 7 convex whorls. Axial sculpture of strong ribs, becoming curved on latter whorls, 11-15 on second-last whorl, fading out at periphery on last whorl; numerous irregular growth lines usually present. Spiral sculpture absent, or present as only microscopic threads. Aperture lens or D-shaped, with broad anterior canal and narrow posterior canal; outer lip expanded, with strong varix externally; inner lip callused, thickened at top and bottom. Colour of axial ribs fawn, interspaces reddish brown, with white spiral band below middle of whorls. Size: Up to 21.8 mm in length. Distribution: Endemic to Australia; Cape Moreton, Queensland, southwards and around southern Australia, to Beachport, South Australia. Habitat: On the continental shelf and slope, 73-405 m. Moderately common. Comparison: The three relatively large Rissoina species from the eastern Australian continental shelf differ in size and sculpture. R. ferruginea is the largest of the three and most strongly sculptured. R. royana is smaller, more slender, with weaker but more numerous axial ribs. R. nielseni is even smaller and almost smooth. R. ferruginea is recorded from deeper water than the other two species. Synonymy: None. Fig. 1: Off Newcastle, NSW, in 148 m (C.unreg) |
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