Schuylkill River. Not common.
Pl. [32], Fig. 7.
Scalares
NITZSCHIA SCALARIS (EHR.) WM. SM.
Valve linear, with obtusely conical apices; costæ transverse, extending more or less to one-third the width of the valve, 3 or 4 in 10 µ; striæ, 9 or 10 in 10 µ, punctate. Length of valve quite variable, up to 480 µ (Cleve).
A well-known form, abundant in salt marshes and more or less brackish water.
Pl. [33], Fig. 6. (To the right of the figure is an outline of the valve reduced one-third.)
Insignes
NITZSCHIA INSIGNIS GREG.
Valve nearly linear or linear-lanceolate; apices broad, slightly produced, obtuse; keel puncta extended into short costæ, 4 or 5 in 10 µ; striæ about 14 in 10 µ. Length variable up to 400 µ.