Diatrype and Diatrypella.

A group of over 60 species.

Fruit-bodies are black or black-brown and from 1mm up to extensive sheets.
They may be isolated disc-like areas or may coalesce to form irregular shapes.

Some are thin crusts, others form elevated masses.

The surface may have tiny bumps caused by the perithecal openings.
In some the surface appears smooth but under magnification the ostioles are visible.

The peritheca are usually erupting through the wood.
The more extensive ones can look like burned wood and a common name for them is tarcrust.