Family I. ZAPHRENTIDAE.--Solitary Palaeozoic corals with an epithecal
wall. Septa numerous, arranged pinnately with regard to four principal
septa. Tabulae present. One or more pits or fossulae present in the
calicle. Typical genera--_Zaphrentis_, Raf. _Amplexus_, M. Edw. and H.
_Streptelasma_, Hall. _Omphyma_, Raf.
Family 2. TURBINOLIDAE.--Solitary, rarely colonial corals, with
radially arranged septa and without tabulae. Typical
genera--_Flabellum_, Lesson. _Turbinolia_, M. Edw. and H.
_Caryophyllia_, Lamarck. _Sphenotrochus_, Moseley, &c.
Family 3. AMPHIASTRAEIDAE.--Mainly colonial, rarely solitary corals,
with radial septa, but bilateral arrangement indicated by persistence
of a main septum. Typical genera--_Amphiastraea_, Etallon.
_Thecidiosmilia_.
Family 4. STYLINIDAE.--Colonial corals allied to the Amphiastraeidae,
but with radially symmetrical septa arranged in cycles. Typical
genera--_Stylina_, Lamarck (Jurassic). _Convexastraea_, D'Orb.
(Jurassic). _Isastraea_, M. Edw. and H.(Jurassic). Ogilvie refers the
modern genus _Galaxea_ to this family.