165 



The Echinoderms were largely represented by many genera that 

 now appear for the first time, belonging to the orders Echinoidea, 

 AsTEROiDEA and Ceinoidea, and well characterise the rocks in 

 which their remains are entombed. 



The Foraminifera are largely represented in the rocks of this 

 period, both in genera, species, and individuals. Some parts of 

 the White Chalk appears to be almost entirely composed of the 

 minute shells of Rotalia, Spirulina and Textularia, mixed with 

 fine pulverulent carbonate of Lime. 



The ZoANTHAKiA are represented by numerous genera of Corals, 

 which, for the most part, belong to the Apoeosa. The family 

 Madreporidce, represented by the genus Discopsammia, which is 

 special to the Chalk, now appears for the first time. The 

 Tabttlata is represented by two genera. The Rugosa, which 

 formed so important a group in the Palaeozoic rocks, is 

 represented in the Lower Greensand by the genus Holocystis. 



I am unacquainted with any evidence of reef-like structure in 

 the Cretaceous rocks of the British Islands similar to those 

 already described in the Oolitic and other older formations, 

 although such may exist in some of the continental stages of the 

 Cretaceous group unknown to me ; as a general rule, however, 

 I think it may be stated that the Cretaceous rocks were deposited 

 under conditions unfavourable to the growth and development 

 of reef-building Corals. Li the following table I have given a 

 list of those genera only, with their distribution, which are 

 special to the Cretaceous period. 



