Ramalina siliquosa, also known as sea ivory,[1] is a tufted and branched lichen which is widely found on siliceous rocks and stone walls on coastlands round the British Isles, occasionally slightly inland. It grows well above the high-tide mark but is still very tolerant of salt spray. The branches are flattened and grey, and bear disc-like spore-producing bodies. It forms part of the diet of sheep in Shetland and on the coast of North Wales. It is found in Iceland where it has a conservation status of a vulnerable species.[2]
The species was originally described as Lichen siliquosus by the botanist William Hudson in 1762. It was transferred to the genus Ramalina by Annie Lorrain Smith in 1918.