34 DB, (1. C. BOURNE ON 



but are not yet developed iuto spines. In the large scar ou the 

 lower surface of the disc, thirty-six septa, corresponding to 

 the thirty-six costss, and a central columella can be more or less 

 distinctly seen, but the iuterseptal loculi and the central cavity 

 are already largely filled up by a compact calcareous deposit, so 

 that the outlines of the septa are blurred and difficult to make 

 out. On the upper surface, on the other hand, there is a 

 distinct calycle in which the septa are conspicuous and the iuter- 

 septal loculi are relatively deep. The centre of the calycle 

 is occupied by a fascicular columella consisting of numerous 

 irregularly shaped calcareous nodules, tbe more peripheral of 

 which are sometimes united with the inner ends of the larger 

 septa, but there are no pali. 



The thirty-six septa are arranged in six systems and four orders, 

 those of the first three orders forming complete cycles. The 

 septa of the first order correspond to the six more prominent 

 costse, are larger and extend further towards the centre of the 

 calycle than those of the other orders. 



The second and third orders are complete, comprising six and 

 twelve septa respectively. The fourth order is incomplete, 

 comprising only twelve septa, and in each system the septa 

 of the fourth order are situated in the loculi between the septa 

 of the first and third ; there are no quaternary septa in the 

 loculi between the secondaries and tertiaries. There is little 

 difi'erence in size between the secondary, tertiary, and quaternary 

 septa. If anything, the tertiary septa are rather longer than 

 the secondary, and in some of the systems the quaternaries are 

 as large as or larger than the tertiaries. 



Though the costse are fairly prominent, the upper edges of the 

 septa stand but very little, if at all, above the level of the disc. 



An outline of one of the primary septa is given in fig. 8 a. It 

 can be seen that the upper edge is horizontally truncated, giving 

 evidence of its recent severance from the corresponding septum 

 of the individual next above it during strobilization. But 

 although the severance is obviously recent, sufficient time must 

 have elapsed for processes of repair and regrowth to have set in, 

 for on the upper margin there are calcareous granules which, as 

 is evident on microscopical examination, have been recently 

 deposited on the truncated edge. Similar granules are discover- 

 able on the upper edges of all the septa, showing that the 

 process of regrowth has already begun. 



