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. 14). 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. 1a) ; 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 of Diplhelia, comprises the 
Oculinide 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 
Oculinidee the septa are entire and exsert, the columella is rudimentary, 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 O. Solanderi; the third is the Caryophyllia multostellata 
of M. Nyst; the fourth is our Diplhelia papillosa. Diplhelia Solanderc, of which a pretty 
good figure has been given by M. Michelin,’ differs from the latter by the existence of 
numerous delicate, vermiculated, longitudinal sulci on its surface.  Diplhelia yaristella” 
differs from D. papillosa, by the calices being smaller and not so deep, by the septa bemg 
thicker, and the columella less developed. _Diplhelia multostellata’ is principally charac- 
terised by the approximation of the calices, and their dilated form. 
Dipthelia 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 Teon. Zooph., tab. xlui, fig. 19. 2 Michelin, loc. cit., tab. xliu, fig. 16, 
5 Nyst, Coq. et Pol. foss. des Terr. tert. de la Belgique, tab. xlviii, fig. 10. 
