THE EOCENE PERIOD: 29I 
Many species are known, and they are particularly character- 
istic of the Middle and Upper of these periods—their place 
Fig. 214.—Nwmmulina levigata. ‘ Middle Eocene. 
being sometimes taken by Ovdcfordes,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 Io,o00o 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—ainto 
the composition of whose central and loftiest parts the Num- 
mulitic strata enter bodily, could have had no existence till 
