The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Frustule elliptical, truncate; valve lunate; median line biarcuate; striæ on dorsal side 10-16 in 10 µ.

Var. libyca (Ehr.) Cl.—Central area distinct on the dorsal side.

Var. pediculus (Kuetz.) Cl.—Central area and nodule quite distinct. Striæ finer than in var. libyca.

Common in ponds. Quite variable.

Pl. [15], Fig. 7.

AMPHORA GIGANTEA VAR. FUSCA A. S.

Frustule elliptical; valve lunate, with straight ventral margin. Axial area absent on the dorsal side; dorsal striæ, 10 in 10 µ, punctate. Ventral part hyaline except at the ends, which are obliquely striated, with short, punctate lines. L. 70-120 µ.

Absecon, N. J.

Pl. [38], Fig. 1.

Diplamphora