BUFFALO SOCIETY OF NATURAL SCIENCES 



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is very abundant in the western part of the Baltic, but is replaced 

 eastward by Bosmina longirostris; another abundant euryhaline form 

 is Podon intermedins. The replacing fresh water types are such as 

 Cyclops quadricornis, Daphnella brachyura, Daphnia quadrangula and 



Fig. i. Sketch Map or Baltic Showing Permillage Variations in Salinity 



Bosmina longirostris (Pouchet and de Guerne, 223, 919, 920). The 

 mollusca show a similar change, the Littorina species, for instance, 

 being replaced by Limnaea, while along the coast where the salinity 

 is low both of these forms live together, and there also N eritina fluvi- 

 atilis, a river form is found. 



