﻿CONTENTS 
  

  

  Introduction 
  f 
  5 
  

  

  Glacial 
  origin 
  of 
  lakes 
  and 
  rivers 
  , 
  6 
  

  

  Mussels 
  of 
  the 
  St. 
  Croix 
  group 
  ? 
  8 
  

  

  Mussels 
  of 
  the 
  Minnesota 
  River 
  group 
  11 
  

  

  Mussels 
  of 
  the 
  Red 
  River 
  group 
  ^ 
  , 
  11 
  

  

  Mussels 
  of 
  the 
  Crow 
  Wing 
  group 
  14 
  

  

  Mussels 
  of 
  the 
  Mississippi 
  group 
  17 
  

  

  Mussels 
  of 
  the 
  isolated 
  lakes 
  20 
  

  

  Summary 
  25 
  

  

  3 
  

  

  