Frustules quadrangular, inflated at the angles, in fasciæ. Valve ovate or lanceolate; striæ moniliform, transverse or slightly radiate; median area or pseudoraphe broad, lanceolate.
DIMEROGRAMMA MARINUM (GREG.) RALFS
Valve lanceolate or linear and inflated in the middle; striæ moniliform, transverse or slightly radiate; median area linear or lanceolate, sometimes not reaching the smooth extremities; striæ, 8 in 10 µ.
Pl. [12], Figs. 9 and 10.
Fig. 9 differs in its lanceolate outline, in having four puncta on each side in a row, and in the striæ which are radiate.
DIMEROGRAMMA SURIRELLA (EHR.) GRUN.
Valve elliptical-lanceolate, with rounded apices; striæ moniliform, radiate; pseudoraphe narrow, lanceolate.
Blue clay.
Pl. [12], Fig. 11.
DIMEROGRAMMA MINUS (GREG.) RALFS