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PSAMMOBIIDAE |
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Gari
lessoni (Blainville,
1826) Description:
Shape elongate-ovate, umbo on midline, anterior end
rounded, posterior squared off; weak broad ridge from umbo to postero-ventral
margin. Exterior with commarginal ridges, coarse dorsally, finer
ventrally, overlaid by numerous, flat, oblique cords that do not extend
onto posterior slope. Interior white and purple, muscle scars
well defined, pallial sinus extending to midline. Hinge right
valve with 2 cardinal teeth, left valve with single bifid tooth.
Ligament
external, attached to nymphs that extend beyond shell margin. Shell
colour purple dorsally (fading with age), white ventrally. Periostracum
thin, brown, more persistent marginally and posteriorly. Size:
Up to 55 mm in length. Distribution:
Indo-West Pacific, including northern Australia. In eastern
Australia, as far south as Sydney. Habitat:
Lives in fine sand or mud, in estuaries and harbours, down to 150
m depth, most commonly in 0-15 m. In Sydney Harbour it was taken in a
range of habitats from the middle reaches, specifically Lane Cove River
and Parramatta River, and downstream to fully marine situations. Comparison:
Gari
lessoni
is a tropical species, overlapping in range with the southern species G.
livida and G. modesta in northern NSW. Compared to those two
species, G. lessoni is larger, higher and has a more truncated
posterior end. Gari lessoni and less obviously G.
modesta possess oblique cords on the anterior and central parts of
the shell, but these are absent in G. livida. Fig.
1:
Gloucester Is., Qld (C.072259) |
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