New Jersey Division of Fish & Wildlife
Endangered & Nongame 
Species Program



        
Key to the Freshwater Mussels
 of the New York Metro Area and New Jersey 


        
1

        
a.  shell with a very sharp posterior ridge, without hinge teeth, shaped like a 
     marine mussel, Mytilus, generally less than 30 mm, and attached to a hard 
     substrate with byssal threads

        
Dreissena polymorpha


        
b.  animal without byssal threads attaching adult to substrate, with or without 
      teeth, not shaped like a marine mussel

        
2

        
2

        
a.   valves with cardinal teeth and two sets of lateral teeth- anterior or posterior

        
3

        
b.   valves with one set of lateral and pseuocardinal teeth, or without teeth

        
4

         
 

        
3

        
a.   valves with serrated lateral teeth; adults greater than fifty mm. in length

        
Corbicula fluminea

        
b.   valves with smooth lateral teeth; generally less than twentyfive mm. in length

        
Sphaeriidae*

         

         
 

        
4

        
a.   hinge teeth absent or nearly absent

        
5

        
b.   hinge teeth present

        
8

         

         
 

        
5

        
a.   beaks not projecting above the hinge line; shell extremely thin

        
Utterbeckia imbecillis

        
b.   beaks projecting above the hinge line

        
6

         

         
 

        
6

        
a.   beak sculpture double looped; pseudocardinal teeth completely absent

        
7

        
b.   beak sculpture concentric and coarse, pseudocardinal teeth 
      represented by a raised thickening near the beaks

        
Strophitis undulatus

         

         
 

        
7

        
a.   nacre salmon or copper colored, shell prominently thickened along the 
      anterior ventral margin below the pallial line

        
Anodonta implicata

        
b.   nacre bluish or white, shell uniformly thin, epidermis often greenish

        
Pyganodon cataracta

         

         
 

        
8

        
a.   lateral teeth absent or reduced, neither functional nor interlocking

        
9

        
b.   lateral teeth well developed, functional and interlocking

        
11


        
9

        
a.   fine transverse ridges on posterior slope present, posterior ridge rounded,
      pseudocardinal teeth reduced and elongate, shell rounded and usually less
      than 70mm long

        
Alasmidonta varicosa

        
b.   fine traverse ridges on posterior slope absent, pseudocardinal teeth strong
      and triangular

        
10

         

         
 

        
10

        
a.   pseudocardinal teeth strong and triangular with rough surfaces, shell small
      to medium, less than 80mm, triangular to ovate

        
Alasmidonta undulata

        
b.   pseudocardinal teeth pronounced and smooth, shell large to 150mm, 
       elongate, oval and kidney-shaped, shell very thick and heavy,
       periostracum blackish

        
Margaritifera margaritifera

         

         
 

        
11

        
a.   right valve with two lateral teeth, shell less than 55mm

        
Alasmidonta heterodon*

        
b.   right valve with one lateral tooth

        
12

         

         
 

        
12

        
a.   height/length less than or equal to 0.48, posterior ridge prominent, 
      posterior end of shell subangular and drawn to a blunt point; pseudocardinal
      teeth elongate and delicate, shell usually less than 110 mm in length

        
Ligumia nasuta

        
b.   height/length greater than 0.48, posterior end not pointed

        
13

         

         
 

        
13

        
a.   nacre may be purple, shell subrhomboid with well defined posterior ridge 
      and slope, very common

        
Elliptio complanata

        
b.   nacre white or colored but not purple

        
14

         

         
 

        
14

        
a.   left valve with small interdental tooth, giving the appearance of three 
      pseudocardinal teeth, shell more or less compressed and subrhomboid  
      in outline, dark green with numerous green rays or brown, adult shell 
      less than 65 mm long, posterior ridge rounded

        
Lasmigona subviridis

        
b.   left valve without interdental tooth, valve appears to have only two 
      pseudocardinal teeth

        
15

         

         
 

        
15

        
a.   adult shell usually less than 80 mm in length, and thin, hardly thicker 
       anteriorly than posteriorly, epidermis dull yellow without rays or with fine 
       rays all over the shell, rays may not be well defined; hinge teeth delicate;
       in or near tidewaters

        
Leptodea ochracea

        
b.   adult shell often greater than 80 mm in length, much thicker anteriorly 
       than posteriorly, may have obvious, well defined broad color rays;
       hinge teeth strong

        
16

         
 

        
16

        
a.   shell without green rays or with green rays restricted to the posterior slope,
      periostracum yellow, clear and glossy

        
Lampsilis cariosa


        
b.   shell with rays all over (may be obscured in old adults), height/length less 
       than 0.60 in males and in most females, posterior ridge  low and rounded, 
       beak not prominent; periostracum greenish and slightly roughened by
       wrinkles parallel to the growth lines

        
Lampsilis radiata

         

        
 * Sphaeridae,  the fingernail or pill clams, are beyond the scope of 
      this handbook
  *  A. heterodon is protected as a Federal and State endangered species, 
     and the killing of this species for any purpose, including identification, 
     is strictly prohibited. In nearly all instances, destructive sampling of 
     metro area freshwater mussels is not necessary for identification and 
     is strongly discouraged; many other area species are protected by state 
     regulation.
     Please visit the Conservation page and the related pages on 
     Permits  and Conservation Status  for more information