1) Family mytilidae 2) Marine mussels 3) Mollusk family 1) Mussels 
The Mytilidae are a family of small to large saltwater mussels, marine bivalve mollusks in the order Mytiloida. The order has only this one family which contains some 52 genera. Species in the family Mytilidae are found world-wide, but they are more abundant in colder seas, where they often form uninterrupted beds on rocky shores in the intertidal...
[n] - marine mussels
family Mytilidae noun marine mussels