54 UNIO. ANODON. DICERAS. 



them is formed of two or three distmct irregular 

 impressions. 



JJnio^ taken chiefly from My a. 



Hyria Mija. 



Anodon Mytilus. 



Iridina Very rare genus. 



" Unio has two teeth on each valve; one is car- 

 dinal, the other lengthened out. The ligament 

 is exterior — the shell pearly. JJnio pictorum 

 is common in rivers. The shell is used to hold 

 small masses of gold or silver for artists, under 

 the name oi sheU-ijold. 



" Anodon is also to be met with in our rivers. 



" A. anatina is eaten by ducks and crows. The 

 latter, when the shell proves too hard to pene- 

 trate, mount with it into the air, and letting it 

 fall, pick out the fish from the broken shell. 



" Chamacea has only three genera. 

 Diceras. 



Cliaina Chama. 



Etheria, a rare genus, from the Indies and 

 Madagascar. 



" Diceras is a fossil genus — only two species 

 known according to Lamarck. 



'' Linnaeus had assembled in his genus, C//«?wrt, 



