CORALS FROM THE LOWER GREENSAND. 71 



so as to constitute by their union a series of complete tabulae, subdivided by the primary 

 septa, and distant from each other about one fifth of a line. Exothecal dissepiments much 

 resembling the preceding ones. Diameter of the calices, and depth of the fossula, about 

 one line and a fourth. 



Fossil from the lower greensand at Redhill cutting, Atherfield, in the Isle of Wight, 

 and at Peasemarsh. 



The specimens here described belong to the Museum of the Geological Society, and had 

 been named by Mr. Lonsdale. The propriety of establishing a new generical division for 

 this remarkable coral, was very judiciously pointed out by that indefatigable palaeontologist ; 

 but, guided by reasons which we do not quite understand, he refers, with a sign of doubt, 

 this same species to the Cyathophora of M. Michelin, a genus which, in our opinion, does 

 not differ from true Stylina. The genus Holocystis differs from our genus Stauria by its 

 extra calicular gemmation, and its costulated walls. It is the most modern representative 

 of the great division of Zoantharia rugosa, which becomes predominant in the Palaeozoic 

 formations, and is principally characterised by the tendency to a quadrate arrangement of 

 the constitutive parts of the Corallites, whereas in the other sections of Zoantharia, six Is 

 the fundamental number of the radiate organs. 



