Family: Unicells or cells loosely attached forming hyphae; cell body varied in shape, a constriction at the center in most species; cell walls consisting of two or more parts, with small pores and various ornaments (Illustrations of The Japanese Fresh-water Algae, 1977).
Genus: Cell body crescent in shape (long, curved, tapered at both ends); cross section rounded; cell wall smooth or with longitudinal lines, bands on the cell wall in some species; chloroplast laminae ridged and radially arranged, which makes cross section star-shaped; pyrenoids aligned or scattered (Illustrations of The Japanese Fresh-water Algae, 1977).

C. acerosum 4 samples 11 clips Japan, 1998	C. aciculare 1 sample 3 clips Higashi-hiroshima Hiroshima, 1998	C. parvulum 2 samples 4 clips Hiroshima, 1998
C. libellula 1 sample 2 clips Hiroshima, 1998	C. lunula 2 samples 9 clips Japan, 1998	C. moniliferum 1 sample 2 clips Nasu-shiobara Tochigi, 1998
C. rectimarginatum 1 sample 2 clips xxxx Pref, Year	C. turgidum 3 clips μm Higashi-hiroshima Hiroshima, 1998	C. turgidum 5 clips μm Higashi-hiroshima Hiroshima, 1998