The Diatomaceæ of Philadelphia and Vicinity

by Charles S. Boyer

Grammatophora subtilissima Bail.

Grammatophora oceanica var. subtilissima (Bail.) V. H., according to De Toni. G. marina and G. oceanica are united by some authors; the latter has more subtle striæ.

Along the coast.

Pl. [8], Figs. 13 and 14.

GRAMMATOPHORA SERPENTINA RALFS

Valve linear-elliptical, long, measuring to 150 µ (De Toni); smooth at the apices. Septum with numerous undulations and hooked at the apex. Puncta in quincunx, 17 in 10 µ.

Along the coast.

Pl. [8], Fig. 21.

GRAMMATOPHORA ANGULOSA VAR. HAMULIFERA (KUETZ.) GRUN.

Frustule nearly quadrate; valve with rounded but not smooth apices. Septum bent into a sharp angle near its origin and ending in a broad hook. Puncta in transverse rows, 14 in 10 µ.