Pl. [31], Fig. 5.
Orthostichæ Cl.
Valve lanceolate or elongated; axial area narrow; central area sometimes apparently dilated into a stauros; striæ punctate, the puncta in transverse and longitudinal rows.
NAVICULA CUSPIDATA KUETZ.
Valve rhombic-lanceolate, with acute ends; axial area linear, narrow, not widened in the middle; striæ transverse, 14-19 in 10 µ (Cl.). L. 70-150 µ.
Blue clay. Not uncommon in fresh water.
Pl. [26], Figs. 1 and 2.
Fig. 2 represents an inner valve or stratum, with strong costæ variable in size, formerly known as Surirella craticula Ehr.
N. cuspidata var. ambigua (Ehr.) Cl.—Valve elliptical-lanceolate, with rostrate ends, smaller than the type and with finer striæ.
Crum Creek.