AMERICAN AND WEST INDIAN FAUNA AND FLORA. 123 



know to be even now growing and increasing in thickness. Yet 

 they have been mentioned by some writers as examples of a 

 former continental extension ; and archaeologists have attempted 

 to find, on the Dolphin and Challenger ridges, the bridges, at 

 depths of nearly two thousand fathoms, of the former land con- 

 nections of Africa and Western Europe with Central and South 

 America. There seems to be no necessity for these supposed 

 Pacific and Atlantic continents, so long as we can explain by 

 more simple causes the distribution of the present fauna and 

 flora. 



The marked difference between the fauna of the Red Sea and 

 of the Mediterranean ^ clearly points to a distinct separation 

 between these seas — greater perhaps than that once existing 

 between the Bay of Panama and the Caribbean — previous to 

 the time when land masses united Malta and Sicily with Africa ; 

 when Crete and Rhodes were united mth Asia Minor, and there 

 was no Eastern Mediterranean to reach the shores of Egypt and 

 Palestine. All this shows a comparatively recent connection 

 of Mediterranean with Atlantic waters, fully supported by the 

 similarity, if not identity, of their marine fauna. We certainly 

 find in the Eastern Mediterranean proof of the great changes 

 which have taken place in the distribution of land and water 

 during the tertiary and diluvial period. These changes, while 

 they may in part be traced to such agencies as denudation both 

 aerial and chemical, must also be referred to terrestrial changes, 

 — to such volcanic or telluric agencies as slowly raise or lower 

 definite tracts of country, when acting undisturbed through 

 long periods of time. We have in the Eastern MecUterranean 

 a district subject to volcanic action, the force of which is 

 marked by the number of active and extinct volcanoes which 

 have produced in the past and are still producing very marked 

 changes. The zdogeographical conditions existing between the 

 northern and southern shores of the Mediterranean do not of 



1 The rapidity with which even slight way to the Mediterraneaiij much to the 



water communications affect the distribu- detriment of the fisheries ; and a species 



tion of species is admirably shown in the of sea-urchin, quite common in the Red 



case of the Suez Canal. Since its com- Sea, has lately been found in the Medi- 



pletion, several species of sharks charac- terranean, near Fort Said, 

 teristic of the Red Sea have found their 



