THE EOCENE PERIOD. 



291 



Many species are known, and they are particularly character- 

 istic of the Middle and Upper of these periods their place 



Fig. 214. Nnmmulina Icevigata. Middle Eocene. 



being sometimes taken by Orbitoides, a form very similar to the 

 Nummulite in external appearance, but differing in its internal 

 details. In the Middle Eocene, the remains of Nummulites 

 are found in vast numbers in a very widely-spread and easily- 

 recognised formation known as the "Nummulitic Limestone" 

 (fig. 10). According to Sir Charles Lyell, "the Nummulitic 

 Limestone of the Swiss Alps rises to more than 10,000 feet 

 above the level of the sea, and attains here and in other moun- 

 tain-chains a thickness of several thousand feet. It may be 

 said to play a far more conspicuous part than any other Tertiary 

 group in the solid framework of the earth's crust, whether in 

 Europe, Asia, or Africa. It occurs in Algeria and Morocco, 

 and has been traced from Egypt, where it was largely quarried 

 of old for the building of the Pyramids, into Asia Minor, and 

 across Persia by Bagdad to the mouths of the Indus. It has 

 been observed not only in Cutch, but in the mountain-ranges 

 which separate Scinde from Persia, and which form the passes 

 leading to Cabul ; and it has been followed still further east- 

 ward into India, as far as Eastern Bengal and the frontiers of 

 China." The shells of Nummulites have been found at an 

 elevation of 16,500 feet above the level of the sea in Western 

 Thibet ; and the distinguished and philosophical geologist just 

 quoted, further remarks, that "when we have once arrived at 

 the conviction that the Nummulitic formation occupies a mid- 

 dle and upper place in the Eocene series, we are struck with 

 the comparatively modern date to which some of the greatest 

 revolutions in the physical geography of Europe, Asia, and 

 Northern Africa must be referred. All the mountain-chains 

 such as the Alps, Pyrenees, Carpathians, and Himalayas into 

 the composition of whose central and loftiest parts the Num- 

 mulitic strata enter bodily, could have had no existence till 



