Includes two species not found in this locality.
9. Perrya.—Valve arched with very sharp central keel; not narrowed in the middle; keel puncta mostly on short or long lines which are sometimes interrupted.
Includes six species not found in this locality.
10. Epithemioideæ.—Keel excentric; keel puncta extended into costæ across the entire valve.
11. Grunowia.—As in the group Epithemioideæ, except that the costæ are shorter, not extending across the valve; keel very excentric.
12. Scalares.—Like Grunowia, but with sharper, somewhat excentric keel; transverse section of frustule quadrangular.
13. Insignes.—Like Scalares, but with more central keel so that many of the forms are near the group Perrya; frustule somewhat sigmoid.
14. Bacillaria.—Keel central or nearly so; valve somewhat arched; keel sharp, as in the group Insignes.
15. Vivaces.—Keel moderately excentric; valve, according to position, semi-lanceolate, with keel puncta in short rows, or lanceolate with quite central keel. The valves have in many positions a resemblance to Hantzschia, so that N. vivax frequently becomes confounded with a form of H. amphioxys. The median keel puncta are not distant and a central nodule is not evident as is the case in all species of Hantzschia.
16. Spathulatæ.—Like the group Bacillaria, but usually with very delicate striated valves; keel in valve view usually bordered with two parallel lines.