Thallus of Lithophyllum racemus encrusting, usually thin. Crusts thick and nodular masses could be formed of many superimposed thalli. The hypothallus, which is the vegetative tissue that lies below the perithallus, is poorly developed or sometimes absent. Each cell develops laterally a curved row of cells which shortly flattens into typical perithallic tissue.The perithallus is the outer layer of the thallus, and it is made up of square to rectangular cells with regular horizontal and vertical partitions between cell rows.