SUBCLASS I 



TETRACORALLA 



83 



(80-130), alternately long and short; the free edges of the longer septa are 



twisted together in the centre to form a pseudo-columella. Tabulae few or 



absent. 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- 



fundum (Owen), 



the type species, 



has often been 



confused with *S'. 



corniculum and 



various species of 



Zaphrentis. 



Zaphrenfis 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 irregular, 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 



Fig. 107. 



Streptdasma profuiulwm (Owen). Cincinnatian Group 

 (Ordovician); Cincinnati, Ohio. Vi- ^, Side view. 

 /;, Transverse section. C, Longitudinal section, (h. 

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



Fig. 109. 



"'■ Zaphrentis cornucopiae 



Zaphrentis cornicula Mich. Calice enlarged. 



Lesueur. Devonian lime- Carboniferous Limestone ; 



stone ; Ohio. Tournay, Belgium. 



Fig. 110. 



Zaphrentis ennislcilleni Nich. Carboniferous Lime- 

 stone ; A, B, Transverse sections through respectively- 

 upper and lower portions of calice. C, 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. 



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



