572 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



Cosmopolitan species 



Foraminifera can be cited as an example of a widely cosmopolitan group. 

 Shokhina, who studed Foraminifera in the Mertviy Kultuk and Kaidak In- 

 lets, has distinguished six deep-water forms for that area belonging to the 

 genera Elphidium, Rotalia and Discorbis. Among them the most frequently 

 met are Rotalia beccarii, Elphidium polyanum and Discorbis vilardeboana. 

 All three forms are widely distributed in the Atlantic and Pacific oceans 

 and the seas connected with them. Nonion depressulum and Elphidium granu- 

 losum, pointed out by Behning, and Ammobaculites pseudospirale, mentioned 

 by Voloshinova, can be added to these six forms. Moreover, Shokhina has 

 discovered four species of plankton Foraminifera : Globigerina bulloides, Gl. 

 triloba, Globorotalia crassa and Globigerinella aegui/ateralis. Hence there are 

 indications that 1 3 forms of Foraminifera have been recorded in the Caspian 

 Sea. The most numerous form, Rotalia, gives on sandy beds up to 2,500 

 specimens and on silt up to 15,000 (in one case 60,000 specimens) per 5 g 

 of soil. The next most common form, Elphidium polyanum, reaches 5,000 

 specimens per 5 g of soil. 



History of the fauna 



Humboldt formulated a theory in the forties of the last century, according to 

 which the Aral-Caspian basin was widely connected with the Arctic Ocean 

 through the western Siberian lowlands by the end of the Miocene epoch. In 

 Suess's opinion a new northern fauna had penetrated into the Sarmatian Sea 

 through this so-called Humboldt Strait. However Suess's theory of the 

 northern genesis of the Sarmatian fauna had no further development and his 

 assumption of the existence of a direct link between the Caspian Sea and the 

 Arctic Ocean to both east and west of the Ural Mountains, at all events since 

 the Eocene period, has been refuted. Th. Fuchs (1887) denied the theory of 

 the northern genesis of the Sarmatian fauna. In his opinion it was an original 

 fauna, evolved in this body of water as a result of its isolation and of the rise 

 in salinity. 



Since it was difficult to derive the Sarmatian fauna from the fauna of the 

 Middle Miocene basin Andrussov and Mushketov deduced that it was 

 evolved from the remains of the Oligocene fauna of the Turanian basin, which 

 had become adapted to less saline water and had migrated from the east into 

 the Sarmatian basin, then in a state of formation. Andrussov assumes that the 

 Sarmatian Sea was populated by (7) forms which arrived from the east, (2) 

 forms which had survived since the time of the Middle Miocene Sea, and (5) 

 forms evolved during the Sarmatian Era. 



The origin of the Akchagyl fauna, which has much in common with the 

 Sarmatian, is just as difficult to trace. The Pontic Sea, which followed the 

 abundantly saline Sarmatian Sea, had lost much of its salinity and was popu- 

 lated by fresh- and brackish-water faunas. This in turn was replaced by a 

 saline Akchagyl Sea, and a rich fauna, similar to the Sarmatian one, appeared 

 in it again. N. Andrussov (1911), and after him I. Gubkin (1931) and A. Arch- 

 angelsky (1932), think that some shelter existed, where the Sarmatian fauna 



