Crusts or cover on rock, or rugged or loose-laying irregularly branched lumps of calcified algae:
Crusts or cover on rock or other substratum 2
Loose-laying lumps of calcified algae, rugged or with stunted branches 7
This is a large group with many species which are difficult to identify. Two species are common and relatively easy to identify:
Lithothamnion glaciale: pink, outgrowths like warts or with stunded branches. Grows in the subtidal as crusts on the rock or as loose-laying lumps (maerl).
Phymatolithon lenormandii: mauvish, relatively smooth surface and normally with a conspicuous white growth zone along the edge. Common in the intertidal.
Crusts or cover on rock mainly in the intertidal 5
Crusts on rock and other substratum in the subtidal 6
Thin and rusty red cover on rock Hildenbrandia rubra
Up to 2 mm thick gelatinous and dark purple crusts in lower part of intertidal (sporophytic stage of Mastocarpus) «Petrocelis cruenta».
Can be several species, and normally fertile structures are needed for identification. A commonly occurring species is Cruoria pellita which can be identified by having zonate tetrasporangia
Loose-laying irregularly branched lumps of calcified algae (maerl); several species, difficult to identify. Common species are: Lithothamnion glaciale, L. corallinoides and Phymatolithon calcareum
