ZOOLOGY : MARINE INVERTEBRATES . 93 



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

 Mytilus edidis 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 







t..'..:~- -Vx* 1 



Asterias. 

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



/' A 



/ / \ 



\ 

 \ 



Cribrella. 

 (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 



