1869.] On a Ternanj Geological Classification. 369 



group. The Upper Greensand may be considered as " a passage- 

 bed " from the sedimentary to the great calcareous central member, 

 the Chalk, a view which seems borne out by the palaeontological 

 relations of the beds, for of the known species 20 per cent, pass 

 up into the overlying beds.* The upper sedimentary member is 

 lost to us, both in Britain and on the Continent, through denudation, 

 for we find the basement beds of the Tertiary series resting every- 

 where on an eroded surface of the Upper Chalk, or of the Maestricht 

 beds. On this point D'Orbigny remarks : — " Pour les limites 

 stratigraphiques superieures (de I'etage Danien) elles sont marquees 

 par des discordances de denudation et d'isolement les plus pronon- 

 cees ;" and as regards the enormous break in time represented by 

 the palaeontological changes Professor Ramsay remarks : — " Of the 

 521 species known in our Upper Chalk, all, with the exception of 

 Terebratula caput-serpentis, and a few Foraminifera, have appa- 

 rently become extinct during that vast period that elapsed between 

 the close of the Cretaceous and the beginning of the Eocene period 

 in England." It is clear, then, that the series is incomplete ; — there 

 is a missing member. 



Tertiary Series. — The Woolwich and Eeading series of Mr. 

 Prestwich together with the London clay, form in England the 

 natural lower sedimentary series of the Tertiary group. These 

 were deposited in a sea open to the north and west, and at the close 

 of this stage a general depression of the middle and south of Europe 

 took place, accompanied by the introduction of the " Middle Eocene 

 series " of Sir Charles Lyell. In the great nummulite limestone 

 formation we cannot but recognize the middle calcareous member 

 of our ternary classification, which has spread over large tracts of 

 Europe, Asia, and Northern Africa, but is absent in Britain. Sir C. 

 Lyell and Viscount d'Archiac have shown that these beds are repre- 

 sented in Belgium and French Flanders by strata characterized by 

 three species of nummulites, which are also more abundantly developed 

 in the limestone formation of the Alps, where it attains a magnitude 

 and characteristically calcareous features unknown in Northern 

 Europe, I regard this as another illustration of development from 

 opposite directions of the calcareous and sedimentary members of 

 the same natural group. 



The upper sedimentary stage is represented by the black shales, 

 marls, and sandstones of Grlarus (" flysch "), and other strata of the 

 Miocene period, of which the " molasse," a great conglomerate or 

 breccia of Switzerland, is the best representative. In England it 

 is doubtful if we have true representatives of this stage, which 

 completes the range of our natural groups and brings us to the 

 confines of the Glacial epoch. 



* See Table v., Professor Ramsay's Address. 



