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Discinisca
The shell is irregularly subcircular in form, ranging from biconvex to concave-convex, with the apexsituated slightly off center. Its external ornament is provided by concentric growth lines; growth occurs multilaterally, in very thin costae. The interior of the animal is characterized by a highly developed musculature consisting of two pairs of muscles, one anterior and one posterior, which serve to close the valves of the shell, and a series of oblique muscled that open them. The pedicle valve contains a subtriangular median ssptum. The animal anchors itself by means of the predicle emerging from the pedicle valve.
The shell of this inarticulate brachiopod is made of calcium phosphate. The example in the photograph measures approximately 1.5 cm (1 1/2- 1 3/4 in).
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