CONTENTS 



CHAPTER VII 



PAGE 



THE CRAYFISH AND ITS ALLIES 97 



APPENDICES : Key to the six chief orders of Malacostraca 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 OligocliEeta . . 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 Echinodermata . 203 



