Frustules biraphid, symmetrical to apical and transapical axes, elliptical to broadly-lanceolate in outline, with ends capitate to acute to rounded or not produced. Striation not resolved to grossly punctate, with or without pseudosepta. Raphe straight, filiform or lateral, isolated puncta present or absent. Central area may be expanded but not thickened into a stauros.
Navicula has traditionally been a genus where species that do not fit into other genera have been placed, making it a large collection of taxa that are probably not interrelated. Taxa within Navicula that have structural similarities have traditionally been placed in subgenera of Navicula (e.g. Patrick and Reimer 1966; Krammer and Lange-Bertalot 1986); many of these have recently been erected to genus status (Round et al. 1990). Although we have followed Round et al. in many of their newly-proposed genera, Navicula, as followed here, is still a diverse (probably unnatural) group.
Light Microscope Image(s)
Each image is accompanied by the genus and species, California Academy of Sciences slide number (ie. CAS 612010), location of the specimen on the slide, and dimension in microns.