90 OUR COMMON BRITISH FOSSILS. 



part of the country there is a classic ground for 

 fossil corals. 



The Permian has yielded very few fossil corals. 

 Chcetetes is said to be found at Humbleton Hill, 

 Durham. 



When we geologize on the limestone beds of the 

 Secondary formations we lose sight of the old-fashioned 

 types of coral, whose generic names by this time have 

 become almost as familiar in our mouths as house- 

 hold words, and we are suddenly introduced to new 

 forms. Many of them are very persistent through 

 the Lias and Oolitic rocks, although other kinds are 

 peculiar to the Chalk. Coral-reefs were abundant in 

 British areas during both the Liassic and Oolitic 

 periods, but not when our White Chalk was formed. 

 The latter appears to have been deposited in deeper 

 water than coral-reefs are built in, and we find the 

 Cretaceous corals are therefore usually of single, 

 non-reef-building kinds. 



Chief among the genera of the earlier Secondary 

 corals are Thamnastraa, Latimceandra, Isastrcea, The- 

 cosmilia, Montlivaltia, Septastrea, Leptophyllia, etc. 

 The latter is plentiful in the Lias rocks in the Isle of 

 Skye, associated with Isastrcea. The number of 

 localities where Lias corals may be obtained is very 

 great. Cowbridge, in Glamorganshire, is one of the 

 best. The visitor to Shakspeare's birthplace at Strat- 

 ford may hammer them out of the beds at Watford 

 Hill, or find them loosely lying on the surface. Fre- 



