NEIDIUM AMPHIGOMPHUS (EHR.) PFITZER
Valve with parallel margins and cuneate ends; striæ transverse, interrupted by several longitudinal lines; central area widened transversely.
Navicula amphigomphus Ehr.
Wissahickon.
Pl. [21], Fig. 14.
NEIDIUM PRODUCTUM (WM. SM.) CL.
Valve linear, elongate, with capitate apices; striæ slightly oblique; longitudinal lines marginal; axial area very narrow, central area small.
Navicula producta Wm. Sm.
Newtown Square.
Pl. [21], Fig. 16.