346 P. M. DUNCAN ON SOME FOSSIL KEEF-BITILDING COKAlS 



The coral-isotherm would have to be 15° of latitude south of its 

 present position in order that reefs should nourish south of Cape 

 Howe ; and this could only be produced by a different distribution of 

 land and sea, and by a different position of the polar axis to that 

 which now prevails. 



A south-polar continent reaching, in the Miocene age, northwards 

 to 50° S. lat., would meet the requirement of a land reflecting the 

 equatorial currents and tides and adding in no way any great 

 amount of cold water ; and large islands off its coast extending to the 

 American and African coast would satisfy most of the biological 

 requirements of the period. To the north and north-east there 

 existed then the land whose memorials are the atolls and fringing 

 reefs of the great Pacific On the other hand there was the open 

 sea, already noticed, of Central Australia, and to the north the 

 great volcanic islands were sea-floors on which Miocene detritus was 

 accumulating. ' Lemuria ' may be assumed to have existed. 



Vast surfaces of South and Central America, and some of North 

 America, were sea-floors ; and the ocean and coral-tracts prevailed 

 over a great space in Europe and Western Asia. Much of North 

 Africa was still submerged. On the other hand there was probably an 

 Atlantis, and a huge continent existed in the north of Central Asia, 

 N. America, and N. and Central Europe. In those days and before, 

 even during the Nummulitic period, the coral-isotherm of 74° E. 

 reached fully 25° IS", of its present possible position in the portion of 

 the globe antipodean to Tasmania ; and the winter's cold could not 

 have been sufficient to chill the surface-water in the latitude of 

 Vienna and "N. Italy. The question arises, — Could the temperature 

 of this broad belt of warm water be maintained by geographical 

 causes alone ? and a second question requires a satisfactory solution, 

 bearing as it does on the question of alternations of season and of 

 light and darkness, — Could such geographical causes as the distri- 

 bution of the land in polar masses and in central islands overcome, 

 in high latitudes, the effects of the position of the globe in relation 

 to the sun in perihelion and aphelion? It appears to me that they 

 might to a certain extent modify the severity of climate, but not 

 sufficiently to permit of important reefs existing in Western, Central, 

 and Southern Europe, and in Tasmania synchronously. That the 

 reefs were contemporaneous, there is every reason to believe. 



An examination of the flora which underlies the marine Cainozoic 

 deposits of the mainland of Victoria has shown that the plants found 

 there resemble those of Tropical rather than of Extra-tropical Aus- 

 tralia ; and as will be noticed in a communication about to be pre- 

 sented to the Society, the Echinodermata of the succeeding strata 

 afford the same kind of evidence. 



The proofs of the existence of higher temperatures, and of the 

 absence of the long and dark months in the Arctic regions, are 

 abundant from the age of the Carboniferous formation to the Mio- 

 cene. During all the ages of the globe down to that period when 

 such vast alterations in the relative level of land and sea occurred, 

 there is found evidence in favour of the theory that perpetual frost 



