X CONTENTS 



CHAPTER VII 



/ PAGE 



THE CRAYFISH AND ITS ALLIES . . . . . . . 97 



APPENDICES : Key to the six chief orders of Malacostraea ' . 122 

 Key to the principal families of Podopthalinata . . . 122 



CHAPTER VIII 



THE DAPHNIA AND ITS ALLIES . . . . . . ' . 125 



APPENDICES : Key to the five orders of Entomostraca . ' . 131 

 Key to the principal families of Cladocera . . . . 131 



CHAPTER IX 



THE EARTHWORM AND ITS ALLIES . . . . . . . 133 



APPENDICES : Key to the principal species of Earthworms of the 



United States <. .143 



Key to the principal families of aquatic Oligochseta . . 144 



CHAPTER X 



NEREIS AND ITS ALLIES . ... . . . . . 145 



APPENDIX : Key to the more important families of Polychseta . 159 



CHAPTER XI 



THE SLUG AND ITS ALLIES . ,. 160 



Key to the three orders of Gastropoda 160 



Key to the principal families of American Pulmonata . . 161 

 APPENDIX : Key to the principal families of marine shelled 

 Gastropods of the Atlantic coast of the United States . .174 



CHAPTER XII 



THE FRESH-WATER CLAM AND ITS ALLIES . . ... . 178 



APPENDIX: Key to the principal families of marine Lamelli- 

 branchiata of the east coast of the United States . . . 188 



CHAPTER XIII 



THE STARFISH AND ITS ALLIES . . . . . . . 192 



APPENDIX : Key to the principal classes of Echinqdermata . 203 



