CYMBELLA HETEROPLEURA (EHR.) KUETZ.
Valve nearly symmetrical, lanceolate, with rostrate, produced apices; median line nearly straight; axial area linear, widened in the middle; striæ radiate, punctate.
Blue clay.
Pl. [18], Fig. 10.
CYMBELLA CUSPIDATA KUETZ.
Valve broad, elliptical, with rostrate, somewhat acute, apices and nearly straight, ventral margin; median line straight, axial area linear, widened in the middle; striæ radiate, punctate.
Blue clay.
Pl. [18], Fig. 17.
CYMBELLA NAVICULIFORMIS AUERSWALD
Valve linear-elliptical, with abruptly produced apices; ventral margin straight; median line almost straight; axial area narrow, central area large, rounded; striæ distant in the middle, closer at the ends.