52 Rupert Jones, on Bivalved Entomostraca. 



successively the Greensand, Gault, and Chalk. The shores 

 were thus gradually changed, and the new land elsewhere 

 raised up, or remaining as islands here and there, bore new 

 plants, new trees, and new animals ; the sea also brought 

 forth new Entomostraca, which may be easily obtained by 

 washing the Gault clay into mud, drying and sifting it, and 

 by washing the Chalk into powder, and examining it with a 

 glass.* 



Another great change occurred over half the world, at 

 least ; the strata that had been accumulating in gradually 

 deepening seas, and on sinking sea-beds, were hoisted up 

 again by subterranean force, and a new era was inaugurated 

 — recognised by geologists in the sands, clays, and limestones 

 which they denominate " Tertiary." The land was diversi- 

 fied more than before, — more islands, more bays, more rivers, 

 more seas; hence a greater variety of life in every shape, 

 animal and vegetable, and not least in Entomostraca. 



From some beds of sand and clays we get Cytheridea 

 Muelleri, such as now covers the estuarine muds not far from 

 mouths of rivers ; in other beds we get Bairdia subdeltoidea, 

 such as is chiefly found in deep seas and warm climates : in 

 another stratum we get the carapaces of Cytheres, such as we 

 find in the shallow water of our oAvn coasts. Here we have 

 evidences of the existence of different conditions of sea- 

 bottoms, contemporaneous or successive, as the case may be, 

 in a series of deposits now converted into clay or stone. 



Elsewhere we have layers of clay or stone filled and covered 

 with the shells of Cyprides, as thickly strewn as in the mud 

 of any river now running. 



Tracing these river-deposits and these sea-deposits, the 

 Geologist traces out the ancient outlines of land and sea in 

 the long past periods of the earth's history, of which we have 

 no other record. But this is a record sufficient; and it 

 teaches us, also, that not only to great things but to small, 

 not only to nionsterb easts — Iguanodons, Elephants, Whales 

 — but to microscopic Entomostraca, is our attention to be 

 turned if we wish to learn aright what has passed on this 

 earth's surface, if we wish to carefully study God's creation, 

 and to see all the evidences of perfect design and perfect 

 adaptation that the history of successive forms of life, Avith 

 their successive modifications of structure and habits, can 

 supply. 



* See some notes on the preparation of clays, sands, and chalk, for micro- 

 scopical purposes, in the ' Geologist,' 1858, vol. i, p. 249. 



