C. E. Gordon — Early Stages in Paleozoic Corah. 117 



(the lower here) is called the " cardinal," and the lower (the upper 

 in figure 10) is called the " counter," Figures 4 and 11 mark 

 an increase in the number of secondary septa, and a noticeable 

 increase in the length of the " cardinal " septum, and a shorten- 

 ing of the " counter " septum. In figure 11 it will be observed 

 how similar the general arrangement of the septa is to that 

 given in figure 15. The lower portion of the median corresponds 

 to {g) in figure 15, the upper to (h). In the upper quadrants the 

 secondary septa (A) in their 19 



relations to the upper pair 

 marked I, follow the plan 

 exhibited in the cardinal quad- 

 rants of figure 15. In the 

 lower quadrants the secondary 

 septa marked (A) and (B), as 

 also do the " primary " septa 

 (Duerden) marked I, have an 

 arrangement that strongly sug- 

 gests the condition in the 

 counter quadrant of figure 15. 

 Figures 5 and 12 show this 

 arrangement even better, and 

 bear a striking similarity to 

 figure 15. There is now evi- 

 dent a striking bilateral arrangement of the septa, which accord- 

 ing to Duerden and Pourtales proceeds from an unsymmetrical 

 development of the secondary septa in only four of six primary 

 interspaces — proceeding as they do on the assumption that there 

 are six primary septa. 



An examination of figures 13 and 14 shows the position of 

 the fossula in Lophophyllum to be in the same position as in 

 the Zaphrentoid coral. To designate the cardinal septum 

 always as the primary septum on the convex side of the coral- 

 lum (after Nicholson) introduces some difficulty in making 

 comparisons. The cardinal septum is to be regarded as that 

 which, with the secondary septa in the same quadrant, exhibits 

 a pinnate arrangement. That this may occur on the concave 

 or convex side of the corallum is well known. According to 

 Jakowlew the one fossula which can be determined is always 

 developed on the cardinal septum.* Both the pinnate arrange- 

 ment of the septa, which marks the position of the cardinal 

 septum, and the fossula are by this author regarded as the 

 product of the mode of growth of the corallum. However 

 thatmay be, we have examples of the fossula and the cardinal 



* " Ueber die Morphologie und Morphogenie der Rugosa," Verbandlungen 

 der Russisch-Kaiserlichen Mineralogischen Gesellschaft zu St. Petersburg. 

 Bd. XLI, Lief 2, 1904. 



Figure 12. Figure 5 inverted. 



