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 le. 
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 trabicule, 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 imdication of radiate coste, whereas in this fossil the corallites, as 
we have already remarked, are quite irregularly grouped, and the surface of the ccenenchyma 
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). 
Dipiuerta papitiosa. ‘Tab. II, figs. 1, la, 1 4. 
Corallum composite, subdendroid, and rather tall. Corailites usually disposed alternately 
in contrary directions, but appearing sometimes irregularly grouped, in consequence of 
two series becoming united so as to forma single branch, or of afew individuals multiplying 
by fissiparity. The cadices placed far apart, quite circular, scarcely prominent, if at all so, 
and united by a highly-developed mural ccenenchyma, the surface of which is covered with 
closely-set, unequal, minute granulations, rather oblong, especially in the vicinity of the 
calices (fig. 1). 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 towards the columella, but do not assume the 
