Shell is narrowly elongated, compressed, and triangular in shape; umbo at pointed anterior end, bluntly flattened or rounded at gaping posterior end. Surface is fragile, sculptured with dense erect scales in younger specimens that erode to smooth areas in older parts of large adults. Exterior is light tan to orange in color; interior lightly nacreous in anterior portion. P. nobilis is the second largest living bivalve, growing to 35.5 in (90 cm) in length. Soft body with pallial organ; secretes long strong stalk of gold or brown byssal threads exiting shell ven-trally near umbo.
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