38-4 



Dr. J. p]. Dueideii on the lielationships 



section through the tip of the corallum displays the median 

 d rk lines of six priniari/ septa, separated by six interseptal 

 spaces. One example exhibits the six septa only (tig. 1), 

 another shows two rudimentary secondary septa in addition 

 to the primary six (fig. 2), while a third presents tour secon- 

 dary septa and the rudiment of a fifth (fig. 3). The sections 

 thus confirm in the most complete manner the statement made 

 by Pourtal^s thirty years ago, and serve to establish beyond 



Transverse section towards the apex of a third coralhira, taken at a little 

 higher level than the two previous sections. The six primary septa 

 are recognizable by their greater size, the outlines being indicated 

 by the oval interseptal loculi and thin marginal lines; the two 

 median septa are now distinct fioni one another, and the upper is 

 larger tlian the lower, and is thereby already recognizable as the 

 main or chief septum. The two upper primary interseptal spaces 

 are much narrower than the middle and lower interspaces. "Within 

 each of the latter an additional septum (A) has appeared, and within 

 the middle right interspace the rudiment of a second additional 

 septum (B) occurs. No new septa are ever developed within the 

 two upper iuter.-eptal spaces. As the calice increases in diameter 

 the angle at which the primary septa are inclined to one another 

 changes, owing to the intercalation of new septa at practicallj* equal 

 distances apart ; hence the irr.gularity in form of the dark median 

 line. In the inward growth of the new septa their inner extremities 

 necessarily come into contact with the older septa already stretching 

 as far as the middle, and thus give rise in lower sections to th« 

 appearance of branching. It is some time before all the septa become 

 rearranged as true independent radii (cp. fig. G). 



a doubt the primary hexameral cliaracter of this one member 

 of the Rugosa. 



The six primary septa are represented in the sections at the 

 tip of the fossilized coral as follows : — A single continuous 



