AGE OF MAMMALS. 265 



money. The nummulites of different beds are of differ- 

 ent species and of various sizes, some of them reaching 

 the size of an inch and a half in diameter. There are, 

 of course, other shells mingled with the nummulites, 

 though some strata are almost entirely nummulitic. 

 " The nummulitic formation," says Lyell, " with its char- 

 acteristic fossils, plays a far more conspicuous part than 

 any other tertiary group in the solid frame-work of the 

 earth's crust, whether in Europe, Asia, or Africa, ft oft- 

 en attains a thickness of many thousand feet, and extends 

 from the Alps to the Carpathians, and is in full force in 

 the north of Africa, as, for example, in Algeria and Mo- 

 rocco. It has also 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 occurs not only in Cutch, but 

 in the mountain ranges which separate Scinde from Per- 

 sia, and which form the passes leading to Caboul ; and it 

 has been followed still farther eastward into India, as far 

 as eastern Bengal and the frontiers of China." In the 

 Swiss Alps nummulitic strata are found 10,000 feet above 

 the level of the sea, and in Thibet at the height of 16,500 

 feet. They enter into the composition of the central and 

 loftiest parts not only of these mountains, but of the Py- 

 renees, the Carpathians, and Himalayas. Where, there- 

 fore, these great mountain chains now are, the sea stood 

 during that long age, when those little animals, the 

 nummulites, were accumulating these vast masses of 

 rock to be raised in after ages into lofty mountains by 

 some of the processes noticed in 226. Though there 

 are some nummulites found in the strata of the same pe- 

 riod in this country, they did not play here the magnifi- 

 cent role in rock-making which they did in Europe, Asia, 

 and Africa. 



373. Tertiary Plants. In the earlier parts of the Ter- 

 tiary period the climate of the earth was more uniform- 

 ly mild than in the latter, and therefore in the strata of 



M 



