31 



of other coralline species, and the development of chambered 

 cephalopods (nautilus, orthoc&ras,) to an enormous size, bearing to 

 the Scottish species somewhat of the same relation as do the 

 Tridacnas of the Eastern seas to the dwarfish bivalves of our north- 

 ern latitudes. The suspended lime, calcareous sand formed of 

 triturated coral, and the countless myriads of testacea, zoophytes, 

 and other creatures with which the waters teemed, united in forming 

 vast deposits of limestone with a prevailing crystalline structure 

 rarely found in the limestones of this age in Scotland. 



Conditions very similar to these prevailed over large tracts in the 

 centre and North of England, where the formation follows the crys- 

 talline type, and has less of that mechanical character which marks 

 the Scottish deposits. Yet are the fossils most markedly alike 

 throughout these groups in the three countries, and all are evi- 

 dently of the same age. We speak, however, rather of the lower 

 groups, the carboniferous limestones of England and Ireland, and 

 the shale and sandstone beds with coal and ironstone seams, in Scot- 

 land. The upper portion of the Scottish series is, we have seen, of 

 fresh- water or estuary origin, and formed under different conditions ; 

 while the upper portions of the Irish series perhaps differ in age from 

 both the others, and in amount of development are far less complete. 



25. For Fifeshire and the Lothians, Mr. Page has recently* 

 given a classification very similar to that set forth by us, but some- 

 what less minute, and perhaps on that account to be preferred in 

 the present state of our knowledge. Founding his deductions upon 

 his own inquiries and the published reports of Mr. C. M'Laren, Sir 

 D. Milne Home, and Mr. Cunningham, he arranges the strata in 

 the following order : 



" 1. True coal measures consisting of numerous alter- 

 nations of coal, shales, sandstones, ironstones, and occa- 

 sional beds of impure limestone, . . -~ . . . 2,500ft. 



"2. Several strata of crinoidal and productus limestone, 

 with intervening beds of shale, sandstones, and thin seams 

 of coal, ... . .180ft. 



" 3. A vast thickness of whitish fine-grained sandstones, 

 bituminous shales, a few thin seams of coal, mussel-bands 

 or shell-limestone, and fresh-water limestones abounding 

 hi cyprides, . . . . , 1,500ft. 



" In this instance there is no development of millstone grit, the 

 whole system resolving itself into upper coal, mountain limestone, 



* In his excellent " Advanced Text-Book of Geology," a work remarkable for accu- 

 rate and clear statement and sober generalization, and adorned by many eloquent 

 passages. 



