Species: Cell body slightly curved, 163-(190-350) μm long, 8-(8.4-13)-20 μm wide, L/W = 25-33; both termini broadly rounded (nearly truncated); cell wall transparent, smooth; 5-7 pyrenoids arranged in a single line (Illustrations of The Japanese Fresh-water Algae, 1977).

C. toxon 2 clips 225 μm L/W=19 Hiroshima, 1998