12 E. HERON-ALLEN AND A. EARLAND ON THE FORAMINIFERA 



Orbitolites complanata still form banks which impede navigation. 

 But speaking generally, the activity of the Foraminifera to-day 

 is displayed in another sphere. In the surface waters of the 

 great oceans the few genera which are found in the pelagic- 

 condition swarm in countless numbers, and their dead shells 

 falling constantly to the sea floor, are there building up layers of 

 Globigerina ooze which, if solidified and raised to the surface,, 

 would be visible as areas of foraminiferal limestone exceeding 

 even the Nummulitic limestones in extent. 



Murray and Renard estimate the area of sea bottom over 

 which Globigerina ooze is at present in process of formation at 

 over 49 1 million square miles. Of its depth we can, of course,, 

 form no idea, but as the great oceans are practically permanent,, 

 it must be very great, because we know from deep-sea deposits 

 which have been elevated into land surfaces in Malta, Barbados,. 

 Trinidad and Australasia, that similar deposits have been forming 

 in the deep sea ever since at least Miocene times. 



Prof. Agassiz has observed (29) : "No lithological distinction 

 of any value has been established between the chalk proper and 

 the calcareous mud of the Atlantic," and it has been reasonably 

 postulated by Prof. Jukes-Brown (30), after a careful analysis 

 of calcareous oozes, that the chalk was deposited in a sea of less 

 than 500 fathoms, though doubtless at a considerable distance 

 from land. The time occupied in the deposit of the English 

 chalk, arguing by the rate at which the Atlantic ooze is 

 formed, which is one foot in a century, must have been 

 150,000 years. 



We cannot but feel that this paper has already overpassed the 

 reasonable limits of such a communication, but our difficulty has 

 been mainly one of selection. The matter is one whose ramifi- 

 cations are almost infinite. A systematic study of the dynamics 

 of the subject remains yet to be completed, though significant 

 beginnings have been made by Prof. Hull and by Prof. Jukes- 

 Brown. A careful consideration of the factors which have led 

 to the deposition of certain forms of Foraminifera and other 

 microzoa in an orderly sequence, dependent for the most part 

 upon current action and specific gravity, must lead us to an 

 understanding of the forces which have accounted for the 

 Building of the World in the form in which we know it. And 

 it is by the study* of such factors, as revealed by their results, 



