280 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rotten blue shales at the foot of Dalahii, and from numerous similar 

 sections, are certainly referable to the Lower Chalk deposits of 

 Europe. 



Other sections will be alluded to showing the position of the 

 Nummulitic Limestones with regard to the Cretaceous equivalents ; 

 and it is especially remarkable, that while the former are compact 

 and crystalline, and contain Nummidites and allied forms of Forami- 

 nifera in abundance, the latter are composed of fawn-coloured fissile 

 layers, which are softer, though sometimes indurated, or of rotten, 

 blue, bituminous shales. 



Although the beds of the two formations are conformable to each 

 other, the characteristic fossils of each never appear together in any 

 intermediate bed. Ammonites only exist in the fawn-coloured layers 

 of limestone and in the blue shales ; but, as soon as these rocks 

 cease and the crystalline limestones succeed in ascending order, the 

 fossil forms are perfectly distinct. How these changes have occurred 

 it is exceedingly difficult to explain ; but certain it is, that such is 

 the fact, and that the crystalline is perfectly conformable to the 

 fissile limestone. 



Altered Nummulitic Limestone. — To the eastward of the deposits 

 thus far described, and extending from Persepolis to near Mount 

 Ararat, are great mountains of highly crystalline, dark-blue, and 

 foetid limestone, in close proximity to the grand central axis of 

 igneous origin, which causes the parallelism of all the exterior ranges. 

 The crystalline and contorted structure of these deposits is neces- 

 sarily to be ascribed to the protrusion or concealed presence of the 

 igneous mass. When stratification is apparent, it is so contorted 

 and crushed that there is no possibility of tracing the beds. Gene- 

 rally all traces of stratification are absent, and the mass is of homo- 

 geneous texture throughout. The colour of the stone is usually 

 dark-blue, but it sometimes varies to light-grey, and even in some 

 cases to white. It is compact, rough to the touch, excessively hard, 

 and heavy, with a saccharoidal fracture, and a bituminous or foetid 

 odour when struck with the hammer. It is a good building-stone, 

 assumes a fine polish, and is equally suitable for internal or external 

 decoration, as is well shown at the deserted and ruined palaces of 

 Persepolis and Siisa. 



When in immediate proximity to the igneous rocks, it becomes 

 almost black, and is traversed by innumerable threads and thin veins 

 of white carbonate of lime. Mountains of this character rise very 

 abruptly from elevated plateaux of rich alluvial soil, and are, as it 

 were, pinched up at their summits into jagged and well-defined 

 angular peaks. Many of the beautiful plains between Ispahan and 

 Hamadan are bounded by picturesque ranges and solitary peaks of 

 this limestone. 



The Rock of Bisiitiin, so frequently described by antiquarians, is a 

 very fine example. 



Mr. Hamilton, in his "Observations on the Geology of Asia 

 Minor" (Quart. Journ. Geol. Soc. vol. iv. p. 367), describes deposits 

 of similarly altered character as occurring to the W. and N.W. of the 



