The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Valve linear-elliptical, broad; axial area broad, widened in the middle; striæ slightly radiate in the middle, 3 in 10 µ; median line oblique, the terminal fissures hook-shaped. L. 86 µ.

Blue clay. Not uncommon.

Pl. [30], Fig. 23.

PINNULARIA BOREALIS EHR.

Valve linear, with rounded or sub-truncate ends; axial area about one-fourth the width of the valve, widened in the middle; median line with large hook-shaped terminal fissures; striæ, 4 or 5 in 10 µ. L. 54 µ.

Blue clay. Occasional in fresh water in a smaller form. Specimens occur intermediate between P. lata and P. borealis.

Pl. [30], Fig. 22; Pl. [31], Fig. 12.

PINNULARIA BOREALIS VAR. SCALARIS (EHR.) CL.

Valve narrow, linear; axial area broad, widened into a transverse fascia; striæ, 8 in 10 µ. L. 32 µ.

Fresh water.