Valve lanceolate extended into beaks or horns curving in opposite directions; keel puncta not evident; striæ, "20-26" in 10 µ. L. 70 µ.
Brackish water. Abundant in Duck Creek, Delaware River.
Valve lanceolate, with beaks or horns about half the length of the median part of the valve; keel puncta, 18 in 10 µ; striæ exceedingly delicate, "about 40 in 10 µ." L. 45 µ.
Frustules like Nitzschia, but enclosed in branching or simple tubes.
Frustule linear, tumid in the middle, obtuse at the ends; valve linear-lanceolate, with somewhat acute apices; keel central or nearly so; keel puncta, 8 in 10 µ; striæ delicate. L. 108 µ.
(named after Dr. Suriray, a physician of Havre)
Valve linear, elliptical or ovate; pseudoraphe linear or lanceolate; a marginal keel forming wings or alæ seen in zone view; costæ short or reaching the pseudoraphe, frequently with intercostal striæ more or less evident.
The genus is divided by Grunow according to the length and form of the costæ. I include Stenopterobia.
Section 1.--Costæ of nearly equal width throughout, reaching the pseudoraphe.
Section 3.--Costæ dilated at the margin, attenuated toward the pseudoraphe.
Section 4.--Valve having the appearance of Nitzschia, with inconspicuous alæ (Stenopterobia).
The endochrome consists of two laminate chromatophores, one on each valve.
The auxospores are single, originating from the union of two frustules (H. L. Smith).
Valve lanceolate, subacute at the ends; costæ robust, about 2 in 10 µ, parallel in the middle, radiate at the ends; pseudoraphe narrow. L. 100 µ.
Pl. 39, Fig. 12; Pl. 35, Fig. 2 (smaller form).
Valve linear, with cuneate ends, slightly constricted in the middle; costæ parallel, 2-3 in 10 µ. L. 90 µ.
Valve oblong-linear, with cuneate ends; pseudoraphe narrow; costæ, 3-4 in 10 µ; striæ, 14-16 in 10 µ, somewhat radiate. L. 34-54 µ.
Fresh and brackish water. Common along the coast.
Valve linear-ovate; pseudoraphe wide; alæ prominent; costæ wide, 1¼ in 10 µ. Frustule in zone view clavate. L. 200-365 µ.
Valve ovate; costæ, 1½ to 2 in 10 µ; pseudoraphe linear, narrow. L. 125-200 µ.
S. splendida is smaller than S. robusta and wider in proportion, but, as intermediate forms occur, it is difficult to distinguish between them.