(A. Schmidt) De Toni 1891 Category: Asymmetrical biraphid
BASIONYM: Cocconema janischii A. Schmidt 1881
SYNONYM(S): Cymbella mexicana var. janischii (A. Schmidt) Reimer
Contributor: Pat Kociolek - January 2011
Length Range: 130-360 µm
Width Range: 35-68 µm
Striae in 10 µm: 6-8
Valves with a highly arched dorsal margin, ventral margin is straight, with a tumid area in the center. The axial area is narrow and slightly enlarged at the center to form an ovoid to irregular central area. The raphe is lateral, with dilated external proximal ends and distal ends deflected towards the dorsal margin. A single stigma is positioned in the central nodule, between the proximal raphe ends. The areolae near the central area are elongated, especially on the ventral side. Striae are radiate and coarsely punctate. Distinct apical pore fields are present at each apex.
Note: The longer valve length indicated here as compared to Patrick and Reimer up to 295 µm, 1975, p. 60) is due to our observation of an initial valve in the sample. Reimer’s suggestion that this species is closely allied with C. mexicana is not supported by published observations, and we have chosen to keep this as a separate species.
Basionym: Cocconema janischii
Author: A. Schmidt 1881
Length Range: µm
Striae in 10 µm:
Bahls, L. L. (2007). Cymbella janischii--Giant endemic diatom of the Pacific Northwest: morphology, ecology and distribution compared to Cymbella mexicana. Northwest Science 81 (4): 284-292.
Cleve, P.T. (1894). Synopsis of the Naviculoid Diatoms, Part I. Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2):1-194, 5 pls.
Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.