Contributor: Pat Kociolek -
Length Range: 19-65 µm
Width Range: 12-55 µm
Striae in 10 µm: 19-23
Valves are broadly elliptical. The raphe valve has a straight, filiform raphe that becomes slightly dilated towards the center. The entire margin of the valve is bordered by a hyaline rim. The axial area is very narrow, and broadens slightly to form a small, irregularly-shaped central area. Striae are distinctly punctate (areolae within a stria number about 19-23/10 µm) and are radiate. The striae are interrupted at the poles, and in larger specimens along a longer stretch, by narrow, irregular lines that are located on both sides of the axial area. The rapheless valve is flexed about the apical axis. The axial area is very narrow, and the central area is small or lacking. Striae are coarsely punctate.
This species is an endemic to the Pacific Northwest.
Basionym: Cocconeis rugosa
Author: Sovereign 1958
Length Range: µm
Striae in 10 µm:
Cocconeis rugosa sp. nov. Pl. III, Figs. 34, 35. Valvae late ellipticae, convexae, 18-63 μ longae, 12-52 μ latae ; rhaphovalva rhaphe directa filiformi, area axiali angustissima, area centrali parva irregulariter definita; striae transapicales radiantes 19-23 in 10 μ, distincte punctatae, puncta etiam 19-23 in 10 μ, praecipue ad polos versus area hyalina longitudinali interruptae ; areovalva area axialis angustissima, area centrali minima, striae transapicales radiantes, 19-20 in 10 μ, distincte punctatae, series punctorum longitudinales paulo remotiores quam striae transapicales, irregulariter undulatae.
Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.
Sovereign, H.E. (1958). The diatoms of Crater Lake, Oregon. Transactions of the American Microscopical Society 77(2):96-134.