Nongeniculate, encrusting, epilithic, coralline; multifilament hypothallium sub-parallel to substratum, mostly arching upward to form perithallium, some filaments arching downward, dead-ending on substratum; cells of adjacent filaments linked by fusions, secondary pit-connections unknown; epithallium thick, 3-14 cell layers (largely dependent on level of invertebrate grazing), epithallial cells with abundant plastids and outermost walls of terminal epithallial cells rounded or flattened but not flared at the corners; meristem intercalary and below epithallium; meristematic cells usually as long as or longer than their immediate inward derivatives; growth (cell division and elongation) and cell wall calcification occurring only in meristematic cells in a narrow (1-2 um wide), often un- or weakly calcified horizontal plane (meristem split) before formation of transverse cell walls; double mode of calcification with primary, small, prismatic, radial calcite crystals within cell walls with secondary, large, diagonal, deltoid inter filament crystals between cell filaments in perithallium; in epithallium interfilament crystals few, vertical and plate-like; all conceptacle fertile discs developed directly from the meristem, sunken at maturity; intersporangial filaments initially calcified, dissolved when sporangia mature; bi/tetrasporangia bearing columnar cap walls (i.e., conceptacles multiporate), roof exposed by sloughing-off overlying epithallium; conceptacle cavity calcite, including surrounding and underlying perithallium dissolved by maturing sporangia; gametangia (where known) and carposporangia (where known) developing in uniporate conceptacles; roof of spermatangial conceptacles not reformed by lateral growing in of tissue, spermatangia produced from columnar cells clothing entire inner walls of conceptacles.

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