The
tabulate corals, forming the
order Tabulata, are an
extinct form of
coral. They are almost always
colonial, forming colonies of individual
hexagonal cells known as
corallites defined by a
skeleton of
calcite, similar in appearance to a
honeycomb. Adjacent cells are joined by small pores. Their distinguishing feature is their well-developed horizontal internal partitions (
tabulae) within each cell, but reduced or absent vertical internal partitions (
septae). They are usually smaller than
rugose corals, but vary considerably in shape, from flat to conical to spherical.