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ISCHNOCHITONIDAE


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Ischnochiton (Heterozona) fruticosus (Gould, 1846)

Description: Animal ovate, elongate, girdle moderately wide. Median valves with lateral and pleural areas well defined; lateral areas raised with strong divaricating ribs; pleural area with criss-crossed fine threads at top, becoming wavy ridges, weak at first, strong towards margin. Girdle densely covered with ridged scales, larger (0.14 mm) at inner edge beside valves, progressively smaller (0.04 mm) towards outer edge. Colour fairly constant; pale greenish, dorsum more pale or with a white stripe.

Size: Up to 40 mm in length

Distribution: Endemic to Australia. Southern Qld, southwards and around southern Australia to Gulf St Vincent, SA, including Tas.

Habitat: Intertidal, under stones, often in muddy situations.

Comparison: This species is similar to Ischnochiton versicolor, but differs by having a fairly constant pale greenish colour, and smaller girdle scales. The girdle scales vary in size, larger on the inward edge of the girdle and smaller on the outer edge, but even the larger scales are only half the size of those in I. versicolour.

Fig. 1: Ulladulla, NSW (C.347150).

Fig. 2: Girdle scales. Same specimen as Fig. 1.

Fig. 3: Valve sculpture. Same specimen as Fig. 1.

 

Copyright Des Beechey 2019