Morphologic Description: Carapace robust, more or less inequivalved, exterior punctate; left valve subovate in lateral outline with highly arched dorsal margin, may have slightly concave posterodorsal segment, both anterior and posterior ends broadly rounded, ventral margin straight and curving upward anteriorly and posteriorly; right valve with distinctly three-segmented dorsal margin showing pronounced angles and more or less concave segments near the two ends, especially produced posterior end, ventral margin slightly indented, anterior end broadly and obliquely rounded, posterior end rather caudate. Anterior and posterior margins of left valve with many small spines, of left valve with very wide but usually ragged straite frills. Hinge elements thick but simple, smooth. Muscle-scar pattern basically consisting of 8 scars in three horizontal to arcuate rows; individual scars are oblong to subcircular in shape and rows are closely spaced; net effect is a compact oval rosette or frequently a nearly complete circle of seven scars surrounding interior eighth scar. Carapace of many species is basically transparent or translucent with an exceeedingly complicated pattern of irregular but consistent opaque areas, each species having its own peculiar pattern. [Paranesidea fracticorallicola Maddocks, 1969] (Maddocks, 1969, p. 39, fig. 16).
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