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Diatoms of the United States is now known as Diatoms of North America.
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Rimmed depression

Having, or approximating, the shape of a rhombus. A rhombus is a parallelogram with all four sides of the same length. Used to describe the shape of a valve (example, Staurosirella rhomboides), a central area, or the girdle view of a frustule (example, Eunotia rhomboidea).

Alternative Term