28 BRITISH FOSSIL CORALS. 



vestiges of an incomplete fourth cyclum often exists. The six systems, independently of 

 these rudimentary septa, are equally developed ; the septa are thin, narrow towards the 

 apex, strongly granulated laterally, of unequal size according to their relative age, scarcely 

 exsert, and terminated by a slightly arched, almost undivided edge. The pali are thick, 

 narrow, and crispate ; they form two coronets, and those corresponding to the secondary 

 septa are rather larger and more distant from the columella than those corresponding to the 

 primary septa. Diameter of the calice, two thirds of a line ; depth of the fossula, half a line. 



A vertical section of one of these corallites (fig. 2a) shows that the walls, as well as the 

 coenenchyma, are of a very compact structure, and are covered with minute granulations ; 

 that the small tubercles arising on the lateral surface of the septa are much less crowded ; 

 that the columella is constituted by small, irregular, filiform, ascending trabiculse, and that 

 the loculi are devoid of dissepiments, or only contain very few of them. 



The genus Oculina, reduced to the limits here assigned to that zoological division, 

 appears to have very few fossil representatives, for this is as yet the only known species 

 belonging to it that is not exclusively recent ; and it might be almost considered as 

 constituting a distinct generic type, for it differs from all the recent species of Oculina by 

 the mode of arrangement of the corallites. In the latter the corallites affect a spiral order 

 in the ascending branches constituted by their union, and the coenenchyma presents near 

 the calices some slight indication of radiate costce, whereas in this fossil the corallites, as 

 we have already remarked, are quite irregularly grouped, and the surface of the coenenchyma 

 is not at all striated. 



Oculina conferta appears to be abundant in the London Clay at Bracklesham Bay. 

 We have received specimens of this fossil from Mr. Dixon and Mr. Frederic Edwards. 



2. Genus Diplhelia (p. xxi). 



Diplhelia papxllosa. Tab. II, figs. 1, la, 1 b. 



Corallum composite, subdendroid, and rather tall. Corallites usually disposed alternately 

 in contrary directions, but appearing sometimes irregularly grouped, in consequence of 

 two series becoming united so as to form a single branch, or of a few individuals multiplying 

 by fissiparity. The calices placed far apart, quite circular, scarcely prominent, if at all so, 

 and united by a highly-developed mural coenenchyma, the surface of which is covered with 

 closely-set, unequal, minute granulations, rather oblong, especially in the vicinity of the 

 calices (fig. la). Calicular margin very thin; fossula large, and very deep. Columella 

 very large, of a spongiose texture, and sub-papillose at the apex. Septa forming three 

 complete cycla, and six equally-developed systems ; very narrow at the upper end, not 

 exsert, thin, granulated on their lateral surface, and presenting along their inner edge 

 delicate denticulations, which become larger towa ; the columella, but do not assume the 



