The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Navicula limosa Donk.

Blue clay.

Pl. [21], Fig. 3 (var. genuina Cl.).

CALONEIS SILICULA VAR. INFLATA (GRUN.) CL.

Valve gibbous in the middle, with rounded ends; central area elliptical.

Schuylkill River.

Pl. [21], Fig. 4.

C. silicula may be recognized by its yellow color when dry. Its varieties are extremely numerous.

CALONEIS TRINODIS (LEWIS)

Valve divided into three segments of equal width; ends cuneate and usually produced; axial area elliptical with a lunate marking on each side; striæ radiate in the middle, elsewhere parallel, about 20 in 10 µ, finely punctate; longitudinal line marginal, scarcely visible; the striæ become fainter toward the axial area.