2:u 



Morjthohgy of the Mudreporaria. 



phvloffcnic relationships of the Antliozoa, and the Rugosa so 

 fai l.ave been found to be remarkably uniform as regards tlieir 

 septal sequence. 



Fig. 5.-A corresponding septum {h„ b) has appeared within each of the 

 ventro-lateral primary chambers. .■, ,, i i. „ j 



Fi- 6.-Another septum (c) occurs withm each middle chamber, and 

 ^ the line of calcihcution of the dorsal and Tentral directive septa (the 

 Gegmseptum or counter septum and the Hauptseptum or cardinal 

 septum) are now discontinuous. 



The fundamental contention raised by Gordon centres in 

 the number of primary septa characteristic ot the iiugosa, 

 that is, whether four or six ; and upon this mainly depends 



