no 



Guide to the Invertelrata. 



Corals. 



6ALLEBY 

 X. 



West Side. 

 Wall- 

 cases 1-6, 

 Table- 

 cases 1-10. 



Cretaceous 

 Corals. 



was once regarded as the only coral of the order Rugosa known 

 later than the Palgeozoic. In spite, however, of its four-rayed 

 symmetry, it is now regarded as a normal Hexacorallum. 



In the Gault, Upper Greensand, and Chalk, the principal corals 

 are small, simple forms, for the muddy sea-bottom of the first, and 

 the cold of the comparatively deep- sea floors of the last, were fatal 

 to reef-builders. The commonest type is conical in shape, such as 

 SmilotrocJms and Parasmilia (Fig. 166c); some species of the latter 



Fio. 166. — Corals of the Upper Chalk, a, Synhelia Sharpeana, M. Edw. 

 i, Stephanophyllia Bowerbankii, M. Edw. c, Farasmilia centralis, Mant. 

 (Prestwich's Geology.) 



are elongate, and become cylindrical, and OncJiotrochus serpentinus 

 is as narrow and sinuous as a worm tube. Another group of 

 forms are discoid, such as Cyclocyathus Fittoni from the Gault, 

 Trochocyathus Harveyanus from the Cambridge Greensand, and 

 Micrahacia coronula from the Chalk. Some specimens oi Axogaster 

 cretacea represent the Gorgonias. 



In the succeeding period, the Eocene, the Gorgonida3 is represented 

 by two more forms — Mopsea costata and Wthsteria crisioides. These 



Fio. 167.— a, Titrbinolia Dixoni, Edw. and H. 

 phylloides, Lonsd. e, Litharcea Websteri, Bow. 

 (Prestwich's Geology.) 



b, Dendrophyllia dendro- 

 M. Eocene: Bracklesham. 



