Valves are rhomboid with a very slight constriction near the rounded poles. The striae are parallel at the valve center, wavy near the apices and slightly convergent at the apices. Striae do not circumradiate the apices. The longitudinal striae are parallel at the valve center, but wavy and convergent near the apices. The longitudinal ribs are constricted at the central nodule. The longitudinal ribs fuse with a linear helictoglossa to form a moderate sized porte-crayon. The external proximal raphe ends form small “T” shapes.
These specimens from Goose Lake, Idaho and Island Lake, Washington appear to have more narrowly rounded apices and finer longitudinal ribs than specimens from the type population from Finland (Lange-Bertalot 2001, pl. 128, figs 1-4).
Author: Lange-Bertalot and Metzeltin 1998
Length Range: 96-135 µm
Width Range: 18-24 µm
Striae in 10 µm: 26-27
Original text and images reproduced with permission by ARG Ganter Verlag KG and Koeltz Scientific Books.
Lange-Bertalot, H. (2001). Navicula sensu stricto, 10 genera separated from Navicula sensu lato, Frustulia. Diatoms of Europe 2: 1-526.
Metzeltin, D. and Lange-Bertalot, H. (1998). Tropical diatoms of South America I: About 700 predominantly rarely known or new taxa representative of the neotropical flora. In: Lange-Bertalot, H. (ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 5. Diversity-Taxonomy-Geobotany. Koeltz Scientific Books. Königstein, Germany, 5:695 pp.