Phymatolithon is a genus of non geniculate coralline red algae, known from the UK,[3] and Australia.

[4] It is encrusting, flat, and unbranched; it has tetrasporangia and bisporangia borne in multiporate conceptacles.

[3] Some of its cells bear small holes in the middle; this distinctive thallus texture is termed a "Leptophytum-type" thallus surface, and has been posited as a taxonomically informative character.

[3] It periodically sloughs off its epithallus, reducing its overgrowth by algae by as much as 50% compared to bare rock.

This Rhodophyta-related article is a stub.