[1] It contains 22 species of corticolous (bark-dwelling) crustose lichens found primarily in tropical regions.

The genus was circumscribed by the British lichenologist Annie Lorrain Smith in 1926, with Stirtonia obvallata assigned as the type species.

These algae belong to the genus Trentepohlia and are responsible for photosynthesis within the lichen symbiosis.

A distinctive feature of Stirtonia is the presence of interascal hyphae (fungal threads between the asci) that anastomose, or interconnect, forming a network.

This thickening results in the internal chambers (lumina) of the spores having a rounded or lens-like shape when viewed under a microscope.