THE DEVELOPMENT AND SEPTAL NOTATION OF THE ZOANTHARIA RUGOSA (TETRACORALLA)

Early investigations by Kunth (1869) of the development of the septa in the Zoantharia Rugosa demonstrated— 1. The serial development of the major septa as opposed to the cyclic development in the Hexacoralla, 2. The four positions of origin of the major septa, 3. The consequent bilaterality of the septal plan, 4. The cyclic development of the minor septa. Later Duerden (1906) and Carruthers (1906) investigating the relationship of the septa considered the first formed six septa to be protosepta sharply distinguished, according to Carruthers, by a pause in development from the subsequently formed metasepta (fig. 1). Faurot (1909) followed by Vollbrecht (1928) and Schindewolf (1931) have since demonstrated that in some forms as Petraia and Cyathaxonia cornu the minor septa have also a serial development (fig. 2). In descriptions of the development of the Tetracoralla various authors have used different symbols to distinguish between the various septa, basing their notation of the septa either on Kunth and differentiating four protosepta, or on Duerden and Carruthers and differentiating six protosepta from the succeeding metasepta. This latter division of the septa has been adopted by Dr. Hill (1935) in her paper on the terminology of the Rugose corals in which paper and those by Professor Schindewolf (1930) a bibliography dealing with the terminology and development of the Zoantharia Rugosa is given. In this paper the author proposes a septal notation which he considers to more accurately represent the septal development and which enables the septal plan of many of the simpler ...