GAMMARUS PULEX. 391 



published by Loven.* These two inland fresh-water 

 lakes are situated on high ground, and have the surface 

 of their waters three hundred feet above the level of the 

 Baltic, whereas the bottom is one hundred and twentv 

 feet below such level. In these lakes (which appear to have 

 been lifted up with the gradual uprising of the country) 

 have been found several genera and species of Crustacea, 

 three of which are Amphipoda, which are affirmed to be 

 identical with marine ones, namely, Gammar 'acanthus 

 loricatus (Sabine, Ross, Kroyer), Pontoporeia affinis (Lind- 

 strom),*f' and Gammarus cancelloides (Gerstfeldt) \. The first 

 is now only known to exist in the Arctic seas, the second 

 in the Baltic, and the last was found in Lake Baikal, 

 in Central Asia. It is therefore suggested by Loven that 

 when the land was raised so as to convert these waters 

 from marine bays into inland lakes, these marine species 

 were retained within the basins, the waters of which have 

 since been changed, through the agency of springs, into 

 fresh-water; and with the gradual transfer of the water the 

 habits of the animals have also changed gradually, and 

 that without any outward alteration of form. Prof. Loven 

 thinks that there is sufficient evidence to show that this 

 change in the conditions of these lakes must have taken 

 place during the great glacial period, at a time when the 



* Of vers, af Kongl. Vet. Akad. 1861, No. 6. 



f Of vers, af Kongl. Vet. Akad. Forkandl. 1855, p. 63. 



% Gerstfeldt, Mem. de l'Acad. de St. Petersbourg, viii. pp. 287-8, be. tab. 



fig. 8. 



Through the kindness of Professor Kinahan, who received them from 

 Prof. Loven, we have had an opportunity of examining specimens of these 

 three amphipoda, and, certainly, except in their being of smaller dimensions, 

 we can perceive no distinction between them and the marine specimens. 

 With the Siberian G. cancelloides, Gerstfeldt, we are not acquainted, but 

 observe that the specimen from Sweden is not a Gammarus, and that it bears 

 no very distant resemblance to Pallasea cancellus (Pallas). Besides the 

 above, the following marine Crustacea have been taken in these fresh-water 

 lakes, My sis relicta, N.S., and Idotkea entornon, L. 



