32 ANNUAL ADDRESS, MDCCCLXXIII. 



combe, along with the old red sandstones. There are 

 about forty distinctive species of fossils which characterize 

 this limestone, of which may be mentioned stringocephalus, 

 megalodon, bronteus, calceola, cyathophyllum. There are 

 fifty-one species of corals enumerated by Mr. Etheridge, 

 none of which are known to have survived Devonian times. 

 A specimen of coral of this age lies on the table. This 

 profusion of corals may well be a strong argument of those 

 who hold that limestones mainly owe their origin to the 

 agency of coral reef builders. 



I now come to the Carboniferous system, and to the 

 limestone to be found in it. At the base of the coal 

 measures in Mid-England, and separated from them only 

 by millstone grit and Yoredale rocks, occurs the Carbon- 

 iferous or Mountain Limestone. Its thickness is greatest 

 in North Staffordshire, and is more than 4,000 feet. Its 

 base has not yet been seen, as the formation happens to 

 make the centre of an anticlinal fold or upheaval, and it 

 has not been broken through. It soon dips beneath the 

 shales and grits on each side of the fold. This limestone 

 occurs in regularly stratified beds, some of them many feet 

 in thickness. It is very hard and compact, generally sub- 

 crystalline, and of a lighter grey colour than the Silurian 

 limestone. In some places it is almost wholly composed 

 of fossils, chiefly crinoids, brachiopoda, and conchifera. The 

 crinoidal portions, when polished, furnish the fossiliferous 

 marble so much used for mantle-pieces, columns, and other 

 ornamentation. The upper beds of this limestone are 

 characterized by being more or less cherty or siliceous. 

 A specimen is on the table. 



At Ashford, near Bakewell, much of the limestone 

 is black, and forms the black marble used for vases 



