Phymatolithon is a genus of non geniculate Coralline algae, known from the UK,[ 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.]
