Mesozoic Geography 333 



which may be opened anywhere, or like a series of superimposed 

 dissolving views of land and sea-scapes. Hence the reconstructed 

 maps of Europe, the only continent tolerably known, show a con- 

 siderable number of islands in puzzling changes, while elsewhere, 

 e.g. in Asia, we have to be satisfied with sweeping generalisations. 



At present about half-a-dozen big connections 1 are engaging our 

 attention, leaving as comparatively settled the extent and the duration 

 of such minor "bridges" as that between Africa and Madagascar, 

 Tasmania and Australia, the Antilles and Central America, Europe 

 and North Africa. 



Connection of South Eastern Asia with Australia. Neumayr's 

 Sino- Australian continent during mid-Mesozoic times was probably a 

 much changing Archipelago, with final separations subsequent to the 

 Cretaceous period. Henceforth Australasia was left to its own fate, 

 but for a possible connection with the antarctic continent. 



Africa, Madagascar, India. The "Lemuria" of Sclater and 

 Haeckel cannot have been more than a broad bridge in Jurassic 

 times ; whether it was ever available for the Lemurs themselves must 

 depend upon the time of its duration, the more recent the better, 

 but it is difficult to show that it lasted into the Miocene. 



Africa and South America. Since the opposite coasts show an 

 entire absence of marine fossils and deposits during the Mesozoic 

 period, whilst further north and south such are known to exist and are 

 mostly identical on either side, Neumayr suggested the existence of 

 a great Afro-South American mass of land during the Jurassic epoch. 

 Such land is almost a necessity and is supported by many facts ; it 

 would easily explain the distribution of numerous groups of terrestrial 

 creatures. Moreover to the north of this hypothetical land, some- 



1 Not a few of those who are fascinated by, and satisfied with, the statistical aspect of 

 distribution still have a strong dislike to the use of "bridges" if these lead over deep 

 seas, and they get over present discontinuous occurrences by a former "universal or 

 sub-universal distribution " of their groups. This is indeed an easy method of cutting 

 the knot, but in reality they shunt the question only a stage or two back, never troubling 

 to explain how their groups managed to attain to that sub-universal range ; or do they 

 still suppose that the whole world was originally one paradise where everything lived side 

 by side, until sin and strife and glacial epochs left nothing but scattered survivors ? 



The permanence of the great ocean-basins had become a dogma since it was found 

 that a universal elevation of the land to the extent of 100 fathoms would produce but 

 little changes, and when it was shown that even the 1000 fathom-line followed the great 

 masses of land rather closely, and still leaving the great basins (although transgression of 

 the sea to the same extent would change the map of the world beyond recognition), by 

 general consent one mile was allowed as the utmost speculative limit of subsidence. 

 Naturally two or three miles, the average depth of the oceans, seems enormous, and yet 

 such a difference in level is as nothing in comparison with the size of the Earth. On 

 a clay model globe ten feet in diameter an ocean bed three miles deep would scarcely be 

 detected, and the highest mountains would be smaller than the unavoidable grains in the 

 glazed surface of our model. There are but few countries which have not been submerged 

 at some time or other. 



