The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Valve elliptical-lanceolate, with apices sometimes rostrate or capitate; pseudoraphe narrow; costæ, 5 in 10 µ.

Common everywhere in pure fresh water and extremely variable.

Pl. [10], Figs. 9 and 10.

Var. elongatum (Ag.) = var. ehrenbergii (Kuetz.)—elliptical-lanceolate, constricted near the apex.

Var. grande (Wm. Sm.) Grun.—linear, elongated, constricted near the apices.

Pl. [10], Fig. 4.

Both of these varieties, with numerous intermediate forms, are abundant near Newtown Square. Varieties of Grunow, known as breve, ovate-lanceolate; productum, ovate-lanceolate with produced apices; capitulatum, lanceolate with capitate extremities, are mingled together in the same gathering.

DIATOMA ANCEPS (EHR.) KIRCHN.

Valve linear with rostrate apices; costæ robust; striæ delicate, 20 in 10 µ. Zone view quadrangular.

Common in fresh water.