308 



NUMMULITIC FORMATIONS. 



[Ch. XVL 



mountain ranges which separate Scinde from Persia, 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. 



Fig. 271. 



Nummulites PuscM, D'Archiac. Peyrehorade, Pyrenees. 

 a. External surface of one of the nummulites, of which longitudinal sections are seen in the 



limestone. 

 &. Transverse section of same. 



Fig. 272. 



NummuMtes 



Sow. Europe and Asia. 



Dr. T. Thompson found nummulites at an elevation of no less than 

 16,500 feet above the level of the sea, in Western Thibet. 



One of the species, which I myself found very abundant on the 

 flanks of the Pyrenees, in a compact crystalline 

 marble (fig. 271), is called by M. d'Archiac 

 Nummulites PuscM. The same is also very 

 common in rocks of the same age in the Car- 

 pathians. 



Another large species (see fig. 272), Num- 

 mulites exponens, J. Sow., occurs not only in 

 the South of France, near Dax, but in Ger- 

 many, Italy, Asia Minor, and in Cutch ; also in 

 the mountains of Sylhet, on the frontiers of 

 China. 

 In many of the distant countries above alluded to, in Cutch, for 

 example, some of the same shells, such as Nerita conoidea (fig. 269), 

 accompany the nummulites, as in France. 



The opinion of many observers, that the Nummulitic formation 

 belongs partly to the cretaceous era, seems chiefly to have arisen 

 from confounding an allied genus, Orbitoides, with the true JSTum- 

 mulite. 



When we have once arrived at the conviction that the nummulitic 

 formation occupies a middle 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 nummulitic strata enter bodily, could 

 have had no existence till after the Middle Eocene period. During 

 that period the sea prevailed where these chains now rise, for num- 



