24 PALEONTOLOGY. 



branched calcareous firm or flexible axis, covered by a fleshy 

 substance strengthened by calcareous spiculse, and serving to 

 lodge the polypes. 



The lamelliferous or stony corals, in which the polypes 

 withdrew into calcareous plaited cells on the surface of a 

 calcareous inflexible axis, are (next to the Testacea) the largest 

 and most important class of invertebrate fossils. They 

 attained a great development in the earliest seas, and were 

 perhaps more widely diffused and individually abundant in 

 the Silurian age than at any subsequent period. "Keef- 

 building" corals are now confined to warm seas, and are 

 wanting even on great tracts of tropical coast. The Oculina 

 is the only large coral now found in the north. But in 

 palaeozoic times the representatives of the modern Astrseas 

 and Caryophyllias extended as far northward as Arctic 

 voyagers have penetrated ; and at a much later period they 

 formed reefs of considerable thickness and extent in the area 

 of the coralline oolite. The Silurian limestone of Wenlock Edge 

 is itself a coral-reef thirty miles in length; and the Plymouth 

 limestone and carboniferous limestone have frequently the 

 aspect of coral-banks skirting the older regions of Cambrian 

 slate and Devonian " killas." The structure of coral-banks 

 may be studied in the lofty limestone cliffs of Cheddar, and 

 in the wave-worn shores of Lough Erne, as well as in the coral 

 islands of the southern seas upheaved by earthquakes of the 

 last century. In the fields about Steeple- Ashton, every stone 

 turned up by the plough is a coral ; and our inland quarries 

 and chalk pits afford to the palaeontologist materials for the 

 study of a class almost wholly wanting on the present sea- 

 shores of Europe. The history of the British fossil corals, as 

 given by Milne Edwards and Haime in the " Monographs of 

 the Palaeontographical Society/' exhibits, equally with that of 

 the fossil shells by other authors, a transition from a state 

 very different from that which now subsists in our part of 



