The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Pl. [22], Fig. 1.

PLEUROSIGMA ÆSTUARII BRÉB.

Valve lanceolate, with produced apices; raphe less sigmoid than the valve and excentric; oblique striæ, 19-21 in 10 µ, at an angle of about 60 degrees.

Along the coast. Common.

Pl. [22], Fig. 7.

(4) Oblique Striæ 60 Degrees, The Transverse More Distant

PLEUROSIGMA RIGIDUM WM. SM.

Valve nearly straight or slightly sigmoid, with obtuse ends; raphe central, excentric near the ends; oblique striæ, 17-21, transverse, 16-19 in 10 µ. (Peragallo).

New Rochelle, N. Y.

Pl. [22], Fig. 2 (very near the var. gigantea Grun.)