These are corals that are now extinct but are known from fossils in both
Paleozoic and Mesozoic rocks. Tabulate corals are characterized by
horizontal partitions called _tabulae_, and septa are absent or poorly
developed. The tabulates were the most abundant reef-building corals
during Paleozoic time and are well known as fossils. Because of certain
similarities with other anthozoans, some paleontologists have treated
the Tabulata as a distinct subclass rather than as an order of the
Zoantharia.
Tabulate corals are not uncommon in many of the Paleozoic rocks of
Texas, and two of these (_Cladochonus_ and _Striatopora_) are
illustrated in Plate 15.