zoology: marine invertebrates. 93 



at all abundant on the rocky shores of this region are the mussels. 

 Mytilus edulis is found in sheltered places, behind rocks and under 

 seaweeds, growing between tides ; while Modiola modiolus may 

 always be found in the pools, where at first it is distinguished with 





Asterias. 

 (After Fewkes, by courtesy of the Essex Institute.) 



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 / / \ \ 



Crlbrella. 

 (After Fewkes, by courtesy of the Essex Institute.) 



difficulty because of the coralline growth upon it. Under stones 

 in the tide-pools may be found also the small Saxicava arctica, a 

 species much more abundant on the Maine coast. 

 The Echinoderms are well represented in the tide-pools. Asterias 



