The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

CYMBELLA CISTULA (HEMPR.) KIRCHN.

Valve cymbiform, with gibbous ventral margin and truncate apices; a distinct row of several puncta occurs below the median line in typical forms.

Blue clay.

Pl. [18], Fig. 3.

CYMBELLA LANCEOLATA (EHR.) KIRCHN.

Valve cymbiform, with gibbous ventral margin; apices truncate; axial area very narrow, scarcely widened in the middle; striæ with fine close puncta.

Kirkwood Pond, N. J.

Pl. [18], Fig. 4.

CYMBELLA MEXICANA (EHR.) A. S.

Valve broad, with gibbous ventral margin and sub-rostrate, truncate apices; median line with reflexed terminal fissures; striæ with coarse puncta; a large punctum occurs in the centre of the central area.