9 



207 



III. Stone Kernels. 



The determination of tliose remains of corals in which the skeleton proper is disinte- 

 grated, leaving only hardened deposits from the inter-septal compartments and occasionally 

 the impression of the outer surface of the coral, presents many difficulties. These remains, 

 too, are the very ones which are found most frequently in our deposits from Danien and 

 senone. They are very common in coral chalk from Faxe and by no means unusual in chalk 

 from Saltholm and Aggersborggaard. Numbers of them have been found in Cerithium chalk 

 from Stevns Cliff. 



These stone kernels from the white chalk are only preserved when they are deposited 

 in flint which prevents their destruction. 



The few species of ramifying corals to be found at Faxe produce stone kernels that are 

 easily recognized by their mode of ramification. It is only necessary then to substantiate 

 this characteristic in orders to determine them. They may, however, be determined even 

 without this. Stone kernels of Dendrophyllia reveal the porous nature of that coral, 

 for all the pores in the theca and its lacunous border are filled with mud in such a way 

 that the upper surface of the stone kernel is covered with an entire layer of a closely lined 

 web of chalk which anastomoses frequently and greatly resembles the tissue of hydro-corals. 



Haplophyllia faxensis has elongated stone kernels with the fillings of the interseptal 

 compartments sharply defined. 



Amfihelia Becki, which like all Oculinae has a tendency to form compact endothecal 

 fillings immediately under the calyces, yields thin, elongated, slightly crooked stone 

 kernels, resembling single corals. 



The stone kernels of single corals present many more difficulties. Stone kernels are 

 formed when mud fills the interseptal compartments. The fillings of the calyces are, there- 

 fore, very intimately connected with the stony mass surrounding the coral, and it becomes 

 almost impossible to analyse these conditions more exactly. Cutting the axis of the coral 

 crosswise gives some information about the inner parts of the septum and the upper parts of 

 the pali and columella; on the other hand cutting destroys part of the stone kernel, so it is 

 advisable to have a large material on hand before resorting to this measure. 



Cutting lengthwise gives information about the lateral surfaces of the septum, about the 

 upper edge of the septum and about columella. 



Among the endothecal formations the dissepiments are recognized by the fact that 

 they hinder the further development of the stone kernel in the interseptal compartments in 

 question, preventing, indeed, the mud from penetrating into the said compartments. If there 

 are many dissepiments present, the stone kernel is short in comparison with the length of 

 the coral, which may be measured by the impression of the theca. If, however, mud succeeds 

 in penetrating beneath the dissepiments, the stone kernel is divided into several sections 

 which lie one over the other. 



Other endothecal formations are difficult to locate, for they disintegrate together 

 with the skeleton proper, leaving no trace. A central formation in the very depth of the 

 coral may occasionally be determined, as for instance incipient columella formation. 



1). K. D. Vidensk. Selsk. Skr , naturv. og niatliem. Afd., 8. Rajkkc. V. 3. 27 



