Blue clay. Fresh water.
Pl. [28], Fig. 1.
PINNULARIA DACTYLUS EHR.
Valve broad, linear, slightly gibbous in the middle; ends broad, rounded; median line not complex, sinuous; striæ, 4 or 5 in 10 µ, crossed by a very broad band. L. ? to 300 µ.
Navicula gigas A. S.
Blue clay. Fresh water.
Pl. [28], Fig. 3.
Forms occur which are with difficulty assigned to either nobilis or dactylus.
PINNULARIA DACTYLUS VAR. DARIANA (A. S.) CL.
Valve linear-lanceolate, obtuse; axial area broad, less than one-third the width of the valve; striæ, 6 in 10 µ, crossed by a broad band. L. 220 µ.