The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Gloucester, N. J. (artesian well).

Pl. [16], Figs. 7 and 8.

ACHNANTHES COARCTATA (BRÉB.) GRUN.

Valves lanceolate, oblong, broad at the ends and constricted in the middle. Stauros wide; pseudoraphe of the upper valve excentric; striæ slightly radiate on the lower valve; puncta small.

Blue clay.

Pl. [16], Fig. 9.

ACHNANTHES LANCEOLATA (BRÉB.) GRUN.

Valves more or less elliptical; striæ radiating, 12 in 10 µ, punctate; on the lower valve a horse-shoe shaped hyaline space on one side of the centre; on the upper valve an irregular stauros, not reaching the margin. L. 8-20 µ.

In springs. Abundant at Newtown Square.

Pl. [16], Figs. 10, 11, 12.