NEIDIUM IRIDIS (EHR.) CL.
Valve linear or lanceolate-elliptical, with sub-cuneate or rounded ends; striæ oblique, about 18 in 10 µ; central area orbicular.
Navicula iridis Ehr.
Navicula firma Kuetz.
Willistown, Pa.; Middletown, Delaware Co., Pa. (Palmer).
Pl. [21], Fig. 17.
The form here figured is probably the variety ampliata (Ehr.) Cl. with less acute apices and more elliptical outline. The species occurs in many variations, the larger being found northward, especially in the peat deposits of New England.
NEIDIUM HITCHCOCKII (EHR.) CL.
Valve linear, with triundulate margin and cuneate ends; striæ transverse, oblique.
Navicula hitchcockii Ehr.