CORALS OF THE LONDON CLAY. 29 



appearance of rudimentary pali. The secondary septa are almost as large as the primary 

 ones, and thus give the appearance of twelve systems (fig. 1 b). Sometimes septa of the 

 fourth order exist in one of the real systems, and in that case the neighbouring tertiary 

 septa become at the same time as large as the elder ones, so that the septal apparatus 

 becomes divided into fourteen almost equal parts. Diameter of the calice, one line ; depth 

 of the fossula, one line, or more. 



The great development and the compact structure of the coenenchyma are rendered 

 manifest by. a vertical section of one of these corallites (fig. la) ; this preparation is also 

 necessary to show the denticulations of the inner edge of the septa, and if continued to a 

 certain distance from the calice, brings to view a few irregular, incomplete, locular 

 dissepiments. 



The new generic division, to which we have given the name 9f Diplkelia, comprises the 

 Oculinidae that multiply by alternate gemmation, and have denticulated, non-exsert, 

 unequal septa, no pali, and a large columella. It differs from Astrhelia by the mode of 

 arrangement of the corallites dependent on the alternate position of the reproductive buds, 

 by the existence of a well-developed columella, and the absence of costal striae near the 

 calices. The mode of gemmation is the same in Amphelia and Enallhelia, but in these 

 Oculinidae the septa are entire and exsert, the columella is radimentary, and the costal 

 striae are well marked near the calices. 



Four species compose at present this small group ; they are all fossil, and belong to the 

 Eocene Fauna. Two of these Corals have been described by M. Defrance, under the 

 names of Oculina raristella and 0. Solanderi ; the third is the Caryopkyllia multostellata 

 of M. Nyst ; the fourth is our Diplkelia papulosa. Dipl/telia Solanderi, of which a pretty 

 good figure has been given by M. Michelin, 1 differs from the latter by the existence of 

 numerous delicate, vermiculated, longitudinal sulci on its surface. Diplkelia raristella 2 

 differs from D. papillosa, by the calices being smaller and not so deep, by the septa being 

 thicker, and the columella less developed. Diplkelia multostellata % is principally charac- 

 terised by the approximation of the calices, and their dilated form. 



Diplkelia papillosa has as yet been found only at Bracklesham Bay, where it appears to 

 be abundant. The specimens here described have been communicated to us by Mr. 

 Bowerbank, Mr. Dixon, and Mr. Frederic Edwards. 



1 Icon. Zooph., tab. xliii, fig. 19. 2 Michelin, loc. cit., tab. xliii, fig. 16. 



3 Nyst, Coq. et Pol. foss. des Terr. tert. de la Belgique, tab. xlviii, fig. 10, 



