The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Hammonton Pond, N. J.

Pl. [34], Fig. 3; Pl. [39], Fig. 9 (zone view).

This, perhaps, is forma sub-acuta Fricke.

Fig. 7, Pl. [34], is probably a small form of S. intermedia, from Willistown, Pa. It resembles a Nitzschia.

SURIRELLA DELICATISSIMA LEWIS

Frustule linear, rounded at the ends; valve linear-lanceolate, sometimes very slightly constricted in the middle, with acute apices; costæ, 5 in 10 µ; striæ about 20 in 10 µ; pseudoraphe well defined, lanceolate. L. to 90 µ.

Fresh water. Newtown Square.

Pl. [34], Figs. 5 and 6 (small forms).

SURIRELLA ARCTISSIMA A. S.

Valve linear, tapering to the sub-acute ends; costæ marginal, 5 in 10 µ; striæ, 18 in 10 µ; pseudoraphe not evident. L. 184 µ.