Reimer in Patrick and Reimer 1975 Category: Asymmetrical biraphid
BASIONYM: Cymbella proxima fo. gravida Reimer in Patrick and Reimer 1975
Contributor: Marina Potapova - March 2012
Length Range: 46-78 µm
Width Range: 17.8-22.5 µm
Striae in 10 µm: 7-8 in the center valve, up to 12 at the ends
Valves are strongly dorsiventral, with broad rounded apices. The dorsal margin is strongly arched, whereas the ventral margin is slightly concave, usually with slightly tumid central portion. The central area is circular and about one third of the valve width in diameter, but somewhat smaller in shorter valves. Three to four stigmata are arranged in a line in the ventral part of the central area. The axial area is narrow, almost central. The raphe is lateral near the middle of the valve, becoming filiform near the distal and proximal ends. The outer and inner raphe slits usually do not appear to cross, but sometimes the proximal and distal raphe ends can be seen as very slightly reverse-lateral. The proximal raphe ends have bulbous central pores that curve to the ventral margin. Apical pore fields are present at both apices. Striae are radiate. Areolae number 14-16 in 10 µm.
Basionym: Cymbella proxima fo. gravida
Author: Reimer in Patrick and Reimer 1975
Length Range: 45-60 µm
Width Range: 20-24 µm
Striae in 10 µm: 8-9 in the center valve, 11 at the ends
Differs principally in shape from the nominate variety. Valves reniform, tapering but slightly from valve center to extremities. Other features as in var. proxima. Striae, 8-9 in 10µ, becoming ca. 11 in 10µ near the extremities. Puncta, ca. 14-15 in 10 µ. Length, 45-60µ. Breadth, 20-24µ.
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.
Cymbella proxima f. gravida has been so far known only from the type locality, Lake Maxinkuckee, Indiana.