pleurosigma

Pleu`ro*sig"ma, n. Etym: [NL. See Pleuro-, and Sigma.] (Bot.) Defn: A genus of diatoms of elongated elliptical shape, but having the sides slightly curved in the form of a letter S. Pleurosigma angulatum has very fine striations, and is a favorite object for testing the high powers of microscopes.

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