PROM THE UPPER AND LOWER WHITE CHALK. 17 



iVOrjE".— CORALS IN FLINTS. 



The flints of the Upper Chalk often contain Corals. Usually the destructive silicification has produced 

 such loss of structures as to render the specific and often the generic diagnosis impossible. No new species 

 have been distinguished in the flints. 



The flint pebbles of the Woolwich series and the basement bed of the London Clay were derived from 

 the Upper Chalk principally. In breaking up a series of the pebbles Mr. J. Flower, F.G.S., discovered 

 several Corals. A cast of a Trochosmilian (Ccelosmilia, sp. — ?) is represented below. 



Cast of a Coral from a pebble. 



Several young simple Corals were noticed by Mr. Flower, but their structures are very badly pre- 

 served. 



Section of simple Corals in flint. 



The most interesting fossil of the series is a perforate Coral, with a most delicate lace-like structure of 

 its ccenencbyma. Within this Coral is an aporose form, probably a Caryoiihyllia. 



Sections of Coral in flint. 



The perforate structure resembles that of the Alveoporse. 



The only example of an aporose Coral which is invariably surrounded by another structure is in Cryptan2;ifl, 

 a genus whose species are always immersed in Celleporee. It is possible that this Caryophyllia of the 

 Chalk was, like Cryptangia parasita, always immersed in a mass of cellular Alveopora. 



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