(A. Mayer) Levkov 2009 Category: Asymmetrical biraphid
BASIONYM: Amphora coffeaeformis var. thumensis Mayer 1919
SYNONYM(S): Amphora thumensis (Mayer) Krieger 1929 | Cymbella thumensis (Mayer) Hustedt 1945
Contributor: Joshua Stepanek - March 2011
Length Range: 9-13 µm
Width Range: 3.8-4.2 µm
Striae in 10 µm: 22-25
Valves are broadly semi-elliptical to semi-circular, with a smoothly arched dorsal margins and convex ventral margins. Valve ends are protracted and capitate. The raphe is located near the ventral margin, straight, with proximal ends straight to slightly dorsally deflected. The axial area is narrow at the poles, widening to form a lanceolate central area. A dorsal fascia is absent. A ventral fascia is present, extending to the ventral margin. Dorsal striae are composed of a single row of areolae, parallel near the central area becoming radiate towards the poles. Ventral striae are radiate near the central area, becoming slightly convergent near the poles.
The systematic position of Halamphora thumensis was under some debate. See Kingston et al. (1980), Krammer (1980) and Levkov (2009) for a thorough discussion.
Basionym: Amphora coffeaeformis var. thumensis
Author: Mayer 1919
Length Range: µm
Striae in 10 µm:
Kingston, J.C., Lowe, R.L. and Stoermer, E.F. (1980). The frustular morphology of Amphora thumensis (Mayer) A.Cl. from northern Lake Michigan and consideration of its systematic position. Trans. Amer. Micros. Soc., 99 (3): 276-283. http://www.jstor.org/stable/3226003
Krammer, K. (1980). Morphologic and taxonomic investigations of some freshwater species of the diatom genus Amphora Ehr. Bacillaria 3:197-225.
Levkov, Z. (2009). Amphora sensu lato. In Diatoms of Europe, Volume 5. (H. Lange-Bertalot, ed). A.R.G. Gantner Verlag K.G. 916pp.
Mayer, A. (1919). Bacillariales von Reichenhall und Umgebung. Kryptogamische Forschungen herausgegeben von der Kryptogamenkommission der Bayerischen Botanischen Gesellschaft zur Erforschung der heimischen Flora 1(4):191-216.
Reported in small abundances in oligotrophic lakes