PONTIC LAKES 



205 



As in the case of the Laramie period, a large number 

 of the freshwater inhabitants of these lakes were descend- 

 ants of freshwater genera, which had been in existence 

 for a long time previously, but some of them were fresh 

 acquisitions from the sea. Cardium, the cockle, was one 

 of these, and gave rise to some new genera under the 



F IG- 72. Congeria, from the Pontic beds. All the 

 figures in this series are reduced a little more 

 than one-half. 1, 2, 3. Congeria subglobosa. 

 4. Dreissenomya aperta. 5, 6, 7. D. Schrcec- 

 kingeri. 8. Congeria Czizeki. 9. C. spatulata. 

 After Neumayr, " Erdgeschichte. " 



changed conditions to which it was exposed ; Adacna is 

 an example. Lithoglyphus, a transformed periwinkle, 

 was another capture. Both this and the cockles still 

 survive in the waters of the Caspian, and Lithoglyphus 

 also inhabits the Danube. The shells which attained the 

 most remarkable development in the Pontic lakes are the 



