The figure represents an unusually large form. It differs from S. ulna only in its apices.
SYNEDRA CAPITATA EHR.
Valve long, linear, dilated into triangular acute apices; pseudoraphe distinct; striæ radiate at the ends.
Blue clay.
Pl. [11], Fig. 8.
SYNEDRA ACUS KUETZ.
Valve very narrow, lanceolate, acicular, with obtuse apices.
Common in the Schuylkill River.
Pl. [11], Figs. 9 and 18.
SYNEDRA GOULARDI BRÉB.