IDOTEA TRICUSPIDATA. 383 



the smaller Crustacea and mussels very readily. It swims 

 swiftly, and when at rest it generally clings to some sub- 

 stance admitting of its supine position ; exuviation ensues 

 at different seasons, the shell being always cast in two 

 portions." 



Mr. Robertson says that, like the herring, they are 

 observed to grow to a larger size in Loch Fyne than on 

 the neighbouring sea-coast. 



