The thallus is gelatinous, sometimes swelling when wet, with a colour ranging from dark olive-green to brown-black, reddish brown or rarely grey-blue.

The texture of the upper cortex surface ranges from smooth to wrinkled or ridged, and is often glossy, but rarely arachnoid.

The underside of the cortex is smooth, arachnoid or hairy, sometimes with scattered hapters or groups of white rhizines.

The photobiont partner is Nostoc (rarely Stigonema), with their cells often arranged in distinct chains.

[5] This is a list of the genera in the Collemataceae, based on a 2020 review and summary of fungal classification by Wijayawardene and colleagues,[1] and including a new genus, Hondaria, circumscribed in 2020.