Vm CONTENTS. 



CHAP. VII. 



The Phytophagous Gastropods continued. — The Turbida?, or Marine 

 Snails - - - ... Page 195 



CHAP. VIII. 



The Phytophagous^Gastropods concluded. — The Haliotida?, or Ear-Shells, 

 and the Naticidae, or Nerits - - - -228 



CHAP. IX. 



On the Aberrant Tribes of the Gasteropoda, — namely, the ,Scutibranchia, 

 or Limpets; the Cyclobranchia, or Chitons; and the Pteropoda, or 

 CrysUl Shells - - - - - - 241 



CHAP. X. 



On the Order Dithyra, or Bivalve Shells. — The Affinities and Analogies 

 of the Unionidae, or River Unios .... 253 



PART II. 



A NATURAL ARRANGEMENT OF THE UNIVALVE AND BI- 

 VALVE SHELL-FISH COMPOSING THE ORDERS GASTERO- 

 PODA AND DITHYRA OF THE CLASS TESTACEA - 295 



EXPLANATION OF TERMS USED IN DESCRIBING THE SHELLS 

 OF TESTACEOUS MOLLUSCA - - - 391 



APPENDIX .. _ _ . 405 



