Cells are small to large, 2- to 12-radiate in end view, with a shallow or deep median constriction. Many species have long hollow processes on each semicell. The processes usually have two or more small terminal spines and often one or more series of denticulations, spines, or verrucae along the processes and on the apex and body of the central axis of the semicell. In species that lack long hollow processes, the semicell angles may be rounded, truncate, or have short processes. The cell wall in these species may be smooth or may exhibit rows of small granules or spinules. There is usually one multilobed chloroplast per semicell, with a central pyrenoid, but several other chloroplast forms and pyrenoid arrangements occur in this genus. The nucleus is in the isthmus.

Toxicity:

Not reported.

Resistence Stages:

Not reported.