CORALS FROM THE CORAL RAG. (es 
exsert, granulated laterally, thick exteriorly, but thin towards their middle part, and their 
upper edge, which is strongly arched, becomes thicker again towards the central part of 
the visceral chamber, but does not quite reach to the columella, so that this last-mentioned 
organ remains quite free to some distance from its upper.end. In some of these composite 
Corals one or two corallites may be found, having the fourth septal cyclum complete, and 
all the system equally developed. 
A transverse section shows that the wad/s of the corallites are very thick, and are 
principally formed by the corresponding part of the sepfa. A vertical section brings to 
light a structure which appears to belong to all the species of the genus Stylina. The 
tissue, which occupies the spaces existing between the cylindrical walls of the corallites, is 
not formed solely by the costa and the exothecal lamin, as in Astrea, but is divided into 
superposed layers, by means of prolongations from the walls which bend down in the 
intercalicular spaces. 
Diameter of the calices, 15 lme; distance between them, 1 or 2 lines, or even more. 
This fossil is found at Steeple-Ashton, Wiltshire, and at Malton, in Yorkshire. The 
British specimens submitted to our investigations belong to the collections of the Museum 
of Practical Geology, the Geological Society, the Bristol Museum, the Cambridge Museum, 
the Paris Museum, Mr. Phillips, and Mr. Bowerbank. Some fossil Corals, which we have 
seen in M. Michelin’s Cabinet, and which were found in the Coralline Oolite of 
St. Mihiel, and some other localitres in France, belong to the same species. 
The genus Sty/ina, as defined in the Introduction to this Monograph, contains a con- 
siderable number of species, and corresponds to no less than eleven genera, lately proposed 
by M. D’Orbigny. ‘These new generical divisions are founded on the differences existing : 
Ist, in the general form of the corallum, which is well known to be very variable; 2d, in 
the depth of the interseptal loculi which that author measured by means of casts, and 
which decreases gradually from one species to another; 3d, in the number of the principal 
septa, which is sometimes six, in other imstances eight, ten, or even twelve, but can always 
be easily explained by slight modifications in the development of the same number of 
septal systems; and 4th, in the axis of the corallites, where the columella is sometimes 
most evident, and in other cases cannot be seen. The absence of a columella in some 
species of Sty/ina would certainly be a character of sufficient importance to justify the 
establishment of a generical division, were it not merely an accident dependent on the 
process of fossilisation, or some other cause independent of the structure of the corallite ; 
but im many instances that is the case. Sometimes, however, we have not. sufficient 
grounds for explaining in this manner the absence of the columella, and we therefore have 
provisionally adopted the genus Cyathophora of M. Michelin, containing the Sty/ina that 
show no traces of that organ ;' but the divisions founded on the various combinations of 
} See our above-mentioned Memoire in the ‘Archives du Museum,’ vol. v, p. 58. 
