Show Origin oi the Isthmus of Suez The Isthmus of Suez has been ascertained to consist of freshwater river formation passing on the south side into marine deposits of the Red Sea and on the north into thoseof the Mediterranean Herr Fuchs has lately studied the question ques-tion how a river came to form a partition between twp seas and their faunas He accepts a theory expressed by Captain Vassel that in the diluvian period the Nile entered the sea in the middle of what is now the isthmus and with its large body of fresh water so filled the narrow strait as to form a true dividing wall between the faunas of the two seas A striking illustration of this mode of action Herr Fuchs finds in the present condition of the straits leading into the Japan Sea viz that between this sea and the sea of Ochotsk on the north the Amur Gulf or Amur Lirnan which is fifteen miles long and three to five broad receives the water of the Amur This river comparable to the Danube has brought much sediment into the gulf and transformed it throughout into a lagoon nowhere more than three fathoms deep quite filled with fresh water Looking at the map one mjght suppose the faunas of the North Japan Sea and the sea of Ochotsk to be in free communication communica-tion with each other but in reality is not so the water of the gulf has only fresh water conchylia and prevents pre-vents exchange between the two marine faunas True the faunas are not so distinct as those of the Red Sea and Mditerranean a certain portion of the Arctic species of the sea of Ochotsk are found south of the Amur Liman There is reason to believe however that these have come not direct through the Amur Gulf but with the Kourile current through the Straits of Sangar in which a large number of these Arctic species are found along with true tropical forms Were this way closed the migration of northern forms would probably be prevented and in that case the two marine faunas might come to be sharply separated as in the case of the Isthmus of Suez London Times |