Page:The Habitat of the Eurypterida.djvu/77

 is very abundant in the western part of the Baltic, but is replaced eastward by Bosmina longirostris; another abundant euryhaline form is Podon intermedius. The replacing fresh water types are such as Cyclops quadricornis, Daphnella brachyura, Daphnia quadrangula and

Bosmina longirostris (Pouchet and de Guerne, 223, 919, 920). The mollusca show a similar change, the Littorina species, for instance, being replaced by Limnæa, while along the coast where the salinity is low both of these forms live together, and there also Neritina fluviatilis, a river form is found.