PROCEEDINGS OF SOCIETIES. 129 



substance. The Lagenida are perforate, but present no inter- 

 stitial canals — the Globigerinida are said to have coarse per- 

 forations and interstitial canals — whilst the Nummulinida 

 present perforations and interstitial canals as well as that 

 peculiar mode of growth already mentioned. Professor 

 Huxley, having had occasion to examine Globigerina himself, 

 states that he does not find the coarse perforations, but the 

 surface presents a series of prismatic outgrowths which 

 might mislead as to their presence. No distinctions of 

 genera and species can be made at all satisfactorily in the 

 Foraminifera. They present great linked and unbroken 

 assemblages of forms. With regard to geographical distri- 

 bution, all the larger species are found in the warmer oceans. 

 Their geological distribution is more interesting. In the 

 Laurentian rocks of Canada, below the great Cambrian 

 series, once called Azoic, Sir William Logan found a struc- 

 ture which Dr. Dawson of Montreal had the great courage 

 to declare organic. This was the Eozoon, which is fairly 

 proved to be an encrusting Foraminifer, such as Carpenteria 

 in its habit, and not unlike Nummulina in structure. In 

 the Lower Silurian beds Ehrenberg detected Foraminifera by 

 internal casts of the chambers of their shells in silicate of 

 iron, which formed a sort of greensand. The shells them- 

 selves were dissolved away. In the Trias they are found, and 

 thence abound in all strata to the present time. But in 

 all this series there is no change in structure or in form ; the 

 species appear to be identical ; in the chalk, at any rate, 

 Globigerina abounds, as it does in the grey chalk now found 

 in the bed of the Atlantic. This is an exceedingly significant 

 fact. The bed of the Atlantic is a vast plain, covered by 

 some 16,000 feet of water; the chalky matter now depositing 

 there is made up of Globigerina, curious little bodies which 

 Professor Huxley called Coccoliths, and five or six per cent, 

 of Radioloria and Diatomese. Whence do they come? Pro- 

 fessor Huxley believes that the Globigerinse live and die at 

 the bottom; but the Radiolarians float while alive at the top, 

 and sink when dead. Vast deposits are made up in the same 

 way as the bed of the Atlantic. The great Nummulitic form- 

 ation belonging to the Eocene period stretches from south 

 England to India, and is made chiefly of the remains of the 

 large Foraminifer Nummulina. The chalk presents exactly the 

 same species as the Atlantic bed, and Mr. Sorby has detected 

 in it even the little Coccoliths found in the Atlantic sea-bed. 

 The siliceous organisms in the chalk have been in great 

 measure dissolved and redeposited in cracks, seams, and 

 cavities ; it is they, in fact, which have furnished the chalk- 

 flints. 



VOL. VIII. NEW SER. K 



