Family: Unicells or cells loosely attached to form 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 flat, large, variable in shape, longer than wide; strong constriction at center; each semicell with several notches; cell wall with many short spines (Illustrations of The Japanese Fresh-water Algae, 1977).

M. apiculata 7 clips 200 x 162 μm Hiroshima, 1998	M. pinnatifida 1 clip 64 x 68 μm Hiroshima, 1998	M. pinnatifida 1 clips 64 x 68 μm Hiroshima, 1998
M. crux-melitensis 4 clips 86 x 86 μm Kuroiso Tochigi, 1998	M. crux-melitensis 2 clips 188 x 150 μm Hiroshima, 1998	M. radiata 3 clips 134 x 124 μm USA, 1999