TINY ROCK-BUILDERS. 153 



complete is the break in the line of Coral history 

 caused by the Permian cataclysm, that the very 

 nomenclature radically changes. 



A good typical specimen of the Liassic corals 

 is the Isastrcea insignis (Fig. 40). Other genera 

 of the earlier Secondary corals are Leptophyllia, 

 Thamnastrcea, Thecosmilia, Montlivaltia, etc. At 

 Lyme Regis, Cowbridge in Glamorganshire, near 



FIG. 40. Isastrcea insignis (Lower Lias). 



Stratford-on-Avon, and at Marton near Gains- 

 borough, Liassic fossils are plentifully obtained. 



Oolitic corals do not differ very much from those 

 of the Lias. Thamnastr&a, Isastrcea, etc., are still 

 abundant, and may;,be~got easily in the quarries near 

 Scarborough. The Coral Rag, whose very name 

 indicates the character of its fossils, is situated 

 nearly at the top of the Middle Oolitic, just above 

 the Oxford Clay. It is not a very thick deposit, 



