RELICT FAUNAS AND LAKES 1063 



salt ; some of these occurrences, like that of the sea-dog, or harbor 

 seal, Phoca. in the Caspian and other seas, had been known pre- 

 viously, and used by Pallas and V. Humboldt to demonstrate the 

 former connection of these lakes with the oceans. Oscar Peschel 

 (41) in 1875 applied the name relict seas {Reliktcnseen) to these 

 bodies of water, which he regarded as derived from the sea by 

 the growth of enclosing land. He and most authors since his 

 time regarded all continental seas containing marine organisms as 

 relicts, even though some of these seas are far inland. Credner 

 (8), however, strongly opposed this view, evidently believing, with 

 Penck, that a distinction should be made between a relict fauna 

 and a relict sea. The former may enter the lake by a process of 

 migration, as is believed to be the case in many instances where 

 the seals (Phoca) are found in fresh water lakes the geologic 

 surroundings of which show that they never were a part of the 

 ocean ; or where a marine fauna has entered a lake basin of inde- 

 pendent origin through a temporary connection with the sea. Such 

 is the case with the Great Lakes of North America, some of which 

 are known to have been temporarily invaded by the sea by way of 

 the Hudson-Champlain depression during early Pleistocenic time, 

 but the origin of which was wholly independent of the sea (16). 

 Thus Lake Ontario was a fresh water lake before it became tempo- 

 rarily connected with the sea. Credner classes as true relict seas 

 all those which at one time were a part of and connected with the 

 oceans. He makes the following divisions : 



L Relict seas due to damming and isolation of parts of the sea, 

 through a growth to above the sea-level of enclosing rock 

 masses, 

 n. Relict seas due to isolation of basin-like depressions in the 

 sea-floor, owing to a negative change in the sea-level. 

 Emersion lakes. 

 HI. Relict seas due to shrinking of former mediterraneans. 



The first division includes (a) coastal lakes due to damming 

 of bays and inlets, by growth of deltas (Lake Akiz), or by the 

 enclosure of bodies of water between the growing delta and the 

 open coast (Lake Pontchartrain and others in the Mississippi 

 delta) ; (b) coastal lakes or lagoons (barachois) due to the growth 

 of sand-bars ( Kurische Hafif) and Ixirrier reefs; (c) atoll seas or 

 coral island lagoons, and others. 



Under the second division are comprised the marginal lakes 

 of the fjord type, as on the coast of Norway, Scotland (Loch 

 Lomond), Iceland (Lagarfljot), and others. Credner classes Lake 



