1859.] GEOLOGY AND MINERALOGY. 347 



" Londoa Clay," the " Bracklesham Beds," and '• Barton Clay," 

 swarm in some places with similar forms, whilst the " Woolwich 

 Beds" below them, and the " Hampstead " and "Osborne" 

 formations of the Isle of Wight, above, are characterised by 

 Cjundonn, Cytheridea, &c., such as love estuaries, lakes and 

 rivers. Lastly, for England, the •' Crag" of Suffolk, and that of 

 Bridlington, abound in marine forms. 



If we had only these little fossils whereby to form an opinion 

 of the probable conditions under which the clays, sandstones and 

 limestones were formed in the long past eras of this planet, we 

 should have, in nearly every case, ample evidence of the history 

 of each bed of mud, silt, and shell-sand, in which these minute 

 Entomostraca can be found. 



The seas of the Silurian period had their thick-shelled Ltper- 

 clitice and Beyricliice very distinct from their now living con- 

 geners, but linked to them by close affinities readily discoverable 

 by the Naturalist. When land was increased, in the Devonian 

 period, the sea-coasts still abounded with marine Crustacea, and 

 the lakes and rivers abounded with Estherim, like those of the 

 present day. The coral-seas, which gave birth to the Derbyshire 

 limestone, abounded with strange forms of Entomostraca. Land 

 still extended, and miles and miles of swampy coasts and lowlands 

 crowded with the dense vegetation of the Coal period, and, inter- 

 sected with black, muddy lagoons, offered a home for endless 

 tribes of Entomostraca, feeding on animal and vegetable refuse — 

 the rotting plants and shoals of fish, poisoned by the black mud 

 of the peaty rivers. These muds and silts, and all their buried 

 shells, and plants, and fish, and crustaceans, sank down, and were 

 covered up and hardened — petrified, often baked by heat, and 

 then, pushed up again by subterranean force, re-appearing at the 

 surface as the hard, rocky base of many a new country, and form- 

 ing the bed of new seas, were eaten into by the ever-working 

 waves, worn down by periodic rains, aided by the scorching sun- 

 beams, the splitting frost, and the incessant agency of the atmos- 

 pheric gases chemically affecting the surfaces of the rock. 



The sea, now occupying fresh areas, contmued its great work 

 of d<^struction and reparation — wearing down the shores to make 

 up the sea-beds ; and it continued to be the abode of life in its 

 myriad forms; but they were mostly new forms. In the new 

 deposits laid down on the upturned edges of the old strata we 

 find Entomostraca again, similar to those of to-day, and in the 



