Bennett and Kociolek 2014 Category: Asymmetrical biraphid
BASIONYM: Halamphora elongata Bennett and Kociolek 2014
Contributor: Jeffery Stone - October 2015
Length Range: 30-66 µm
Width Range: 8.0-13.7 µm
Striae in 10 µm: 19-23 dorsal at center; 22-26 dorsal at ends
Valves are semi-elliptical and strongly dorsiventral. The dorsal margin is highly arched. The ventral margin is usually weakly concave, but is slightly tumid near the central nodule in larger specimens and nearly straight in smaller valves. Valve ends are subcapitate, ventrally curved and slightly protracted. The raphe is positioned near the ventral margin. The raphe branches are typically straight, but may be slightly curved dorsally from the poles toward the central area. Proximal raphe ends are expanded and dorsally deflected; distal raphe ends have a short dorsal deflection. The axial area is a narrow, often arched or semi-circular hyaline area on the dorsal side of the central nodule. In larger valves (> 60 µm), the hyaline area may be greatly expanded. Dorsal striae are finely punctate, with dash-like areolae that radiate throughout. Distinctly thickened virgae and widely-spaced striae are present between the proximal raphe ends. Ventral striae are short and difficult to see in LM, especially in the in central area.
Under the SEM, short striae can be seen on the ventral margin (Kociolek et al. 2014).
Basionym: Halamphora elongata
Author: Bennett and Kociolek 2014
Length Range: 31-50 µm
Width Range: 8-11 µm
Striae in 10 µm: 19-23 at dorsal ends, more widely spaced at mid-valve; 26-30 ventral mid-valve
Valves with smoothly curved, convex dorsal margin. Ventral margin slightly convex. Ends protracted narrowly, rostrate to capitate. Length 31- 50 μm . Breadth 8- 11 μm. Axial area linear or linear-lanceolate, wide. Central area asymmetric to rounded formed by an interruption of the ventral striae and more or less shorten striae on the dorsal side. External proximal raphe ends rounded; external distal raphe ends curving dorsally over the last two dorsal striae. Dorsal striae radiate less numerous and more widely spaced at mid-valve, 19- 23/10 μm with dash-like puncta. Ventral striae composed of short dashes 26-30/10 μm.
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Kociolek, J.P., Laslandes, B., Bennett, D., Thomas, E., Brady, M. and Graeff, C. (2014). Diatoms of the United States 1: Taxonomy, Ultrastructure and Descriptions of New Species and Other Rarely Reported Taxa from Lake Sediments in the Western U.S.A. Bibliotheca Diatomologica 61, J. Cramer, Stuttgart.
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NADED ID: 9098009
Halamphora subcapitata was collected from modern shallow (~3 m water depth) sediment surfaces from Foy Lake, Montana. Foy Lake has a slightly elevated conductivity (1.1 mS/cm).