Dictionary entry

Pleurosigma

Webster's Dictionary 1913

‖Pleu′ro‐sig″ma (?), n. [NL. See Pleuro-, and Sigma.] (Bot.) 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.