126 BRITISH FOSSIL CORALS. 
primary ones ; the others developed proportionally to the age of the cyclum to which they 
belong, except in the systems where a fifth cyclum exists, for there the septa of the fourth 
cyclum are nearly as broad as the tertiary ones. Pali twelve in number, well developed, 
equal in size, and always corresponding to the tertiary septa, the existence of the incomplete 
fifth cyclum not appearing to have any influence on their position. Diameter of the 
corallum eight or nine lines ; height three lines. 
We have not as yet been able to examine any well-preserved specimens of this fossil, 
and although we have ascertained the existence of characters that separate it generically 
from all other corals, we are not quite satisfied respecting its real zoological affinities. We 
have been induced to consider it as belonging to the family of Zurbinolide, and indeed it 
closely resembles Cyathinine by the great development of the pali; but in one specimen 
we have perceived some appearance of dissepiments, and consequently, when better 
known, the genus Discocyathus may prove to be an Astreida. 
D. Eudesi is the only specimen belonging to this genus. It was figured for the first 
time by M. Michelin, but from specimens so deeply imbedded in the matrix, that no 
satisfactory idea of their form could be obtained. In our Monograph of the Zurbinolide 
we have given a new figure of the same species taken from a fossil belonging to the collec- 
tion of M. Defrance at Sceaux, but it must be noted that this species which shows the 
calice very well, presents a complete fifth cyclum, a circumstance which does not usually 
occur. 
Discocyathus Eudesi is found on the Inferior Oolite in Dorsetshire, at Burton 
Bradstock and Greenland, and, in France, at Bayeux and Port en Bessin. The British 
specimens here described belong to the collections of Sir H. De la Beche and Mr. Walton. 
Genus TROCHOCYATHUS, (p. xiv.) 
Trocnocyataus Maenrviniianus. Tab. XXVI, figs. 1, la, 14. 
TurBINoLia MAGNEVILLIANA, Michelin, Icon. Zooph.,’p. 8, tab. ii, fig. 2, 1840. 
— (vRocHocyaTHUS?) MaGNEVILLIANA, Milne Edwards and J. Haime, Monogy. 
des Turbinolides, Ann. des Se. Nat. 
s. 3, vol. ix, p. 335, 1848. 
ApLocyatuus MaenevituiaNna, D’Orbigny, Prod. de Paléont., vol. i, p. 291, 1850. 
TrocnocyaTuus MaGNEVILLIANA, Milne Edwards and J. Haime, Polyp. Paleoz., &e., p. 23, 
1851. 
Corallum simple, free, hemispherical; its basal surface presenting a central dimple 
surrounded with a small elevated edge, and a smooth circle. Coste straight, granulose, 
striated transversely, almost flat, but somewhat thicker and slightly prominent near the 
calice, and rather unequal in size alternately, or from four to six. Sepa exsert, somewhat 
