''Phymatolithon'' is a genus of non
geniculate coralline red algae, known from the UK,
and Australia.
It is encrusting, flat, and unbranched; it has tetrasporangia and bisporangia borne in multiporate
conceptacle
Conceptacles are specialized cavities of marine and freshwater algae that contain the reproductive organs. They are situated in the receptacle and open by a small ostiole.Boney, A.D. (1969). ''A Biology of Marine Algae''. Hutchinson Educational ...
s.
[ 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.][ It periodically sloughs off its epithallus, reducing its overgrowth by algae by as much as 50% compared to bare rock.]
References
Red algae genera
Corallinales
{{Rhodophyta-stub