516 ANCIENT CORAL-FORMATIONS. 



was gradually changed by the process just described. Further, 

 the collections of other animal remains are such, as we should 

 expect to find on the margin of a coral reef or island existing at 

 that epoch ; and a similar process of fossilization is taking place 

 at this very time, on the shores of the islands now being built up, 

 the species of animals imbedded being, however, not the same. 

 The great thickness of the beds of this rock may be very well ac- 

 counted for, in the same manner as the depth of the coralline masses 

 of recent formation ( 1141). The Oolite had its origin in the 

 wearing-down of the older limestone beds, with additional matter 

 derived from the skeletons of the races of animals which existed 

 during the period of its formation. And there can be little doubt 

 that the C%a/-formation owes a considerable part of its substance 

 to the same sources ; though part was doubtless derived from the 

 decomposition of shells, and a large proportion in some situations 

 from the remains of animals of extreme minuteness, presently to 

 be described ( 1222). There are observed, in rocks of more 

 recent formation, appearances which still more clearly indicate 

 that they too were originally formed by Coral-polypes. These 

 are often found within narrow limits, as if they had been reefs 

 or islands of small size. Thus we find a stone, called Coral- 

 rag, in Oxfordshire ; and very distinct Coral-beds in the Crag 

 of the eastern coast of England. It is interesting to remark, 

 that the remains of Coral, which are found in the older lime- 

 stones, all correspond with those at present abounding near the 

 equator, and exhibit the Lamelliform structure ( 1135) ; whilst 

 they are gradually replaced, in the newer strata, by species more 

 allied to those at present existing in temperate climates. This is 

 one of the many facts which tend to prove that this part of the 

 earth had at some former period a much higher temperature than 

 at present. 



