rBCLASS I 



TETRACORALLA 



83 



10-130), alternately long and short; the free edges of the longer septa are 

 'isted together in the centre to form a pseudo-columella. Tabulae few er 

 )sent. Position of the cardinal septum is recognisable on the exterior by the 

 System of pinnately diverging costal ridges. Common in Ordovician and 

 Silurian. S. pro- s a k 

 fundmn (Owen), 

 the type species, 

 has often been 

 confused with S. 

 corniculum and 

 various species of 

 Zaphrentis. 



Zaphrentis Raf . 

 (Caninia Mich. 

 pars) (Figs. 108- 

 10). Simple, tur- 

 binate or sub- 

 cylindrical, fre- 

 quently elongated. 

 Calice deep, with 



circular margin. Septa numerous, reaching to the centre ; cardinal septum in a 

 deep fossula. Tabulae numerous; somewhat irregulär, and passing from side to 

 side of the visceral chamber ; dissepiments sparingly developed in outer zone 

 of corallum. 50 to 60 species known, ranging from Silurian to Carboniferous. 

 Maximum development in Carboniferous. 



Amplexus Sow. Simple, sub-cylindrical or elongated turbinate. Calice 



Streptelasma profundum (Owen). Cincinnatian Group 



(Ordovician); Cincinnati, Ohio. 



Side view. 



B, Transverse section, C, Longitudinal section. (h, 

 Cardinal septum ; g, counter septum ; s, alar septum.) 



Fig. 108. 



Zaphrentis cornlcxda 

 Lesueur. Devonian lime- 

 stone ; Ohio. 



Fig. 109. 



Zaphrentis cornucopiae 

 Mich. Calice enlarged. 

 Carboniferous Limestone ; 

 Tournay, Belgium. 



Fig. 110. 



Zaphrentis enniskilleni Nich. Carboniferous Lime- 

 stone ; A, B, Transverse sections through respectively 

 Upper and lower portions of calice. (', A long and two 

 Short septa united at the ends to form the wall. D, 

 Longitudinal section showing tabulae (after Nicholson). 



shallow, usually with septal fossulae. Septa moderately numerous, short, 

 never produced to centre. Tabulae highly developed, horizontal. Ordovician 

 to Lower Carboniferous. Type, A. coralloides Sow. 



Aulacophyllum E. and H. Turbinate. Septa numerous, extending to 



