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Austrocochlea rudis (Family Trochidae)

Smooth Top Shell

Distribution:

The Smooth Top Shell has a south-western Australian distribution. It ranges from SA to the Murchison River, just north of Geraldton in WA (SA, WA).

Features:

The Smooth Top Shell has a solid and turban-shaped shell that has a high spire. Its shell exterior is smooth. Its height and width are about equal. It grows to a length and height of 35-40 mm. The aperture is strongly lirate, meaning it is shaped like a lyre. Inside the aperture are narrow, angled ridges. Small raised points called denticles or teeth occur on the hinge line. The operculum tightly fits the aperture and this allows this shell to live high on the shore. The columella is smooth or has a low nodule at the base. It has a closed umbilicus.

The shell's colour is dark purple-grey with a dark green to black inner lip. The columella and aperture are white. Its spire is often eroded to white.

Ecology/Way of Life:

The Smooth Top Shell is common to abundant at mid to low-tide levels on rocky shores. The smooth and dark Austrocochlea rudis appears to be a south-west equivalent of the strongly ribbed, light grey Ribbed Top Shell, Austrocochlea constricta, the most common top shell in southern Australia, or the striped Zebra Top Shell, Austrocochlea porcata, which is abundant in south-eastern Australia.

Interaction with Humans/Threats: The Smooth Top Shell is extremely common in south-western Australia and occurs in many locations far from the influence of human habitation. It is therefore probably not under risk. However, it is not a well-researched species and there is a paucity of information on its lifestyle compared with the other south-eastern Austrocochlea species.

Other Comments:

Austrocochlea rudis, Gray, 1826. Other synonyms are Austrocochlea melanoloma, Menke, 1843, and Austrocochlea torri, Cotton & Godfrey, 1934.

Further Reading:

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. p.90, New Holland Press, Sydney.

Wells, F. E. & Bryce, C. W. (1988). Seashells of Western Australia. p.76, Western Australian Museum.

Wilson, B. (1993) Australian Marine Shells. Prosobranch gastropods. Odyssey Publishing.

Wilson, B. R. & Gillett, K. (1979). A Field Guide to Australian Shells: Prosobranch Gastropods. p.36, Reed.

Acknowledgments:

Text, map & photograph by Keith Davey.

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