New York Metropolitan Region and New Jersey
Freshwater Mussel Identification Handbook


Mussel Features
Growth Lines

Note: In temperate latitudes such as the metro region growth lines are laid down annually.
Complete growth lines may thus be counted to approximate mussel age.

     
 

     

    
Growth lines vary among 
species, appearing as
concentric circles of 
ridges or contrasting
bands of color that 
mark the stages of
growth.

    
Anodonta implicata
alewife floater 

    
Ligumia nasuta
   eastern pondmussel 

     
 

     
 

     

     
 

     
 

     

    
The color and texture
of the periostracum may
conceal or highlight
the pattern and color
of the growth lines.


    
Lampsilis cariosa
   yellow lampmussel 

    
 Pyganodon cataracta
eastern floater

     
 

    
View other features
Anterior and Posterior
Beak and Beak Sculpture   Color Ray
Growth Lines   Hinge Teeth
Length, Width, Height, Profile, Silhouette 
 Posterior Ridge and Slope  
Shell Shape

    
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Mussel Features Menu
Front Page 
  Introduction to Mussels  
Species Menu    Key
Conservation and Monitoring
Bibliography   Glossary