You have a true mussel (Family Mytilidae), of which there are presently no introduced species in the Nordic Waters.
For more information see the Introduction to mussels and false mussles
You may use data, pictures,information etc. available ad the site, as long as you refere to the sourse.
The database as a whole is to be cited as follows:
NOBANIS. Available from http://www.NOBANIS.org. Data of access x/x/201x