(W. Smith) Kirchner in Cohn 1878 Category: Asymmetrical biraphid
BASIONYM: Cocconema parvum W. Smith 1853
Contributor: Loren Bahls - May 2016
Length Range: 25-41 µm
Width Range: 6.9-8.9 µm
Striae in 10 µm: 10-12 at the valve center, up to 14 near the apices
Valves are lanceolate and dorsiventral with narrowly rounded, unprotracted apices. The dorsal margin is moderately arched; the ventral margin is slightly convex to nearly flat in the smallest specimens. The axial area arched and located ventral to the valve mid line. The central area is a slightly wider continuation of the axial area. Proximal raphe ends are reverse-lateral, deflected ventrally, and terminate with inflated pores. Terminal raphe fissures are deflected dorsally at about 45 degrees. Striae are slightly radiate at the valve center, becoming more strongly radiate near the apices. Areolae number 24-28 in 10 µm. A single isolated stigma (occasionally 2) is located at the end of the median stria on the ventral side.
Basionym: Cocconema parvum
Author: W. Smith 1853
Length Range: µm
Striae in 10 µm:
Kirchner, O. (1878). Algen. In: Kryptogamen-Flora von Schlesien im Namen der Schlesischen Gesellschaft fur vaterländische Cultur (F. Cohn, ed.). Zweiter Band, Erste Hälfte. J. U. Kern, Breslau. 283 pp.
Krammer, K. (2002). The genus Cymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 3: 1-584.
Smith, W. (1853). Synopsis of British Diatomaceae. John Van Voorst, London 1853. 89 pp., pls 1-31.
Specimens of C. parva pictured on this web page are from Logging Creek, a mountain stream on the west side of Glacier National Park, Montana. On the date of collection, Logging Creek had a pH of 7.74 and a specific conductance of 50 µS/cm. Krammer (2002) reports this taxon as a nordic-alpine species that prefers oligotrophic waters with lower to average electrolyte content. Illustrations by Smith (1853) show that this taxon lives in colonies and produces branched and unbranched stalks.