LOWER PALEOZOIC TETRACORAL FAMILY COLUMNARIIDAE
BY R. S. BASSLER
Since the uncertainty regarding the genotypes of many rugose coral (Tetracoralla) genera has been removed by the publication in 1940 of the Index of Paleozoic Coral Genera by Lang, Smith, and Thomas, research upon this group can now proceed upon a firm basis. Many of the older Tetracoralla have been assigned to the Cyathophyllidae, characterized mainly by radially arranged septa, although other family names have been proposed for special sections of this one and then abandoned as synonyms. The discovery that the oldest known compound coral, Tetradium simplex Bassler, from the Ozarkian rocks of Maryland, is a Lichenaria exhibiting the simplest type of structure in the Columnariidae, a family long ago separated from the Cyathophyllidae by Nicholson, suggests the following evolutionary trend. Lichenaria with tabulae but without septa gives rise to Lyopora and also to Nyctopora, the latter with the septa . . .