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, wt are not quite satisfied respecting its real zoological affinities. We 

 have been induced to consider it as belonging to the family of Tiirbinolida, and indeed it 

 closely resembles Cyathinina 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 om* Monograph of the Tiirbinolida 

 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. 



Biscocyathus 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.) 



Trochocyathus Magnevillianus. Tab. XXVI, figs. 1, \a, lb. 



TuRBiNOLiA Magnevilliana, Mickelin, Icon. Zooph., p. 8, tab. ii, fig. 2, 1840. 



— (trociiocyatuus?) Magnevilliana, Milne Edwards and J. Hainie, Monogr. 



des Turbinolides, Ann. des Sc. Nat. 

 s. 3, vol. ix, p. 335, 1848. 

 Aplocvathus Magnevilliana, B'Orbiyvy, Prod, de Pak'ont., vol. i, p. 291, 1850. 

 Trochocyathus Magnevilliana, Milne Edwards and /. Ilaime, Polyp. Palscoz., &c., p. 23, 

 . ' 1851. 



Corallum simple, free, hemispherical; its basal surface presenting a central dimple 

 surrounded with a small elevated edge, and a smooth circle. Cosfa straight, granulose, 

 striated transversely, almost flat, but somewhat thicker and shghtly prominent near the 

 calice, and rather unequal in size alternately, or from four to six. Sejjfa exsert, somewhat 



