ScHARFF — On the Origin of the European Fauna. 459 



The Arctic seal {Fhoca annellata), which, as tvg have learned, is 

 closely allied to the Caspian seal, is also found in the Gulf of Bothnia, 

 and in Onega and Ladoga lakes, bnt is quite absent from the remainder 

 of the Baltic and the west coast of Scandinavia. We have a similar 

 case of distribution in the four-horned sting-fish ( Cottvs quadricornis) 

 which inhabits the White Sea and then again the Baltic as far south 

 as Gothland, and also the lakes Wetter and Wener in Sweden, but 

 does not occur on the west coast of Scandinavia. Its principal food 

 consists in the isopod Idotea entomon, which also inhabits the Caspian, 

 and is a typical marine form. It occurs in many of the Eussian, 

 Finnish, and Swedish lakes, and also in the Baltic, but is absent from 

 the west coast of Scandinavia. Perhaps the best known form, with a 

 similar range, is the schizopod Mysis relicta. It is clearly a descen- 

 dant from the Arctic Mysis oculata, of which it was formerly con- 

 sidered a mere variety. The araphipods, Gammaracantlius relictus and 

 Pontoporeia affinis, are two additional well-known Arctic Crustaceans, 

 whose European range differs but little from those above mentioned. 

 But there are others (see Dr. Norquist's writings (64)). 



Rudolph Leuckart first applied the name " Reliktenseen " to such 

 lakes as the north Bussian ones and the Swedish, containing marine 

 organisms, and supposed to have been flooded by, or to have been in 

 close connexion with the sea at some former period. Loven, 0. Peschel, 

 and others worked out his views more in detail, and strengthened his 

 position in regard to the Beliktenseen. More recently Dr. Norquist 

 (64) strongly defended these views, and so has Prof. Sars (75a, 

 p. 124), who remarks, when referring to Pontoporeia affinis, that "it 

 constitutes most probably a remnant of the ancient Arctic fauna, 

 existing off th.e coasts of Europe and JS'orth America during the Glacial 

 Period, a part of which still remains in the more isolated marine 

 basins, as the Baltic ; whereas another part, by the subsequent rising 

 of the land, was left behind in some of the lakes, where the present 

 species, under certain circumstances, was enabled to adapt itself to 

 live in purely fresh water." 



While recognizing the claims of some of the Swedish lakes to be 

 looked upon as "Reliktenseen," Prof. Credner (19) denies altogetlier 

 that either the Onega or the Ladoga lakes can be regarded as belong- 

 ing to that class, or indeed that the Baltic ever had any connexion 

 with the White Sea. Moreover he does not believe that the occur- 

 rence of marine organisms in inland lakes can be adduced as a convinc- 

 ing proof of the marine origin of such lakes. His chief contention 

 against the relic theory is the fact that marine molluscs are entirely 



E.I.A. PKOC, SEK. m., VOL. IV. 2 K 



