L.S. - Tangential section reveals the wide dissepimentarium and the tabularium with incomplete domed tabulae intersecting with the major septa. The calice is usually only a few millimetres across, and is round, elliptical or polygonal in shape. Axial structures are quite rare. Tabulates generally lack septa or dissepiments. If septa are developed, they take the form of about 12 septal spines arranged around the periphery of each corallite.
Colonies occur in both fasciculate and massive forms.
While most colonies are reasonably small, some forms are known to develop hemispherical masses a metre or more in diameter. Fasciculate forms may have corallites branching irregularly, and may be joined at intervals by connecting pores or tubes. Some massive forms have mural pores - communication holes in the corallite walls. Numerous complete horizontal tabulae are usually present. Members of this order are a major component of mid-Palaeozoic reefs.