FRAGILARIA ARCTICA GRUN.
Valve oblong or elliptical, 10 µ in length; striæ subtle, with coarse, short striæ at intervals on the margin and evident in zone view.
Marine. Common at Cape May, N. J.
Pl. [10], Figs. 22 and 23.
FRAGILARIA UNDATA WM. SM.
Valve in general outline linear-elliptical, with extremities produced; striæ subtle; pseudoraphe distinct.
Fresh water.
Pl. [10], Figs. 24, 25, 27, 28 and 29.
FRAGILARIA LINEARIS CSTR.
Valve linear, with rounded apices; striæ subtle; pseudoraphe indistinct.