Valve biconstricted, with large, rounded, sub-truncate apex and broad, sub-truncate basis; striæ, 9 in 10 µ, radiate in the middle, alternately longer and shorter, transverse at the basis and near the apex where they again radiate, coarsely punctate, puncta, 12 in 10 µ. Axial area linear; central area rounded, with several large stigmas in a longitudinal row; terminal fissures hook-shaped.
Blue clay.
Pl. [19], Fig. 4.
GOMPHONEMA LANCEOLATUM VAR. INSIGNIS (GREG.) CL.
Valve lanceolate; axial area narrow; central area unilateral with one stigma; striæ with coarse and distant puncta.
Common and variable.
Gomphonema insigne Greg.
Pl. [19], Figs. 6 and 12.
Fig. 12 shows a unilateral central area. Fig. 6 is more clavate in outline with small central area. In both forms the coarse puncta are in distinct longitudinal lines in the middle.
GOMPHONEMA ACUMINATUM VAR. TURRIS (EHR.) CL.?