THE EUROPEAN SEAS. 



283 



European area, it may serve to throw some light on 

 the real nature of the changes which have gone 

 before, if we select one instance and illustration 

 of the manner in which the members of an existing 

 fauna become the evidences of the date of physical 

 change. 



The Black Sea fauna, as has been seen, is an ex- 

 tension of that of the Mediterranean ; along the 

 whole of the north coast of the Black Sea, from 

 Bessarabia, across to the north-west of the Crimea, 

 and about Kertch, the deposits now forming, and 

 which contain the remains of the existing Black Sea 

 testacea, overlie consolidated beds, which were ac- 

 cumulated beneath the waters of the great Aralo- 

 Caspian Sea (p. 209). The waters of this vast area 

 were fresher than are those of the Aral Sea now, and 

 the dead shells of the present beaches of the Black 

 Sea are in striking contrast with the fresh-water 

 forms which occur in the cliffs — such as Paludina, 

 Limncea, Neritina, Melanopsis. 



This fresh-water fauna is of great antiquity, 

 and though vast physical changes have occurred 

 since it first made its appearance in this area, it is 

 not as yet extinct ; at least, not wholly so : the 

 fossil JVeritince and Driessence are identical with 

 those now found in the Danube and the Don ; and 

 the aberrant forms of Cardium, such as C. plicatum, 

 C. coloratum, and C. pseudo-car dum, still linger about 

 the mouths of the rivers which now flow into the 



