CONTENTS. XI 



PAGE 



ropods, 106 : Pectinibranches, 106108 : Tubulibranches, 108 : 

 Scutibranches, 108 : Cyclobranches, 108 : Acephales testaces, 108 

 110: Acephales sans coquilles, 110 : Brachiopods, 110, 111. . . 99 



LETTER VIII. 



The locomotion of the Mollusca : connection between the shell and 

 animal, 113 : the muscles, 114. Swimmers : the Pteropods, 114 118 : 

 the Heteropods, 118, 119 : the Cephalopods, 119, 120 : the Nautilus, 

 121 123 : the Paper Nautilus, or Argonaut, 123125 : the Salpse 

 and Pyrosomae, 125, 126. Crawlers : the Cephalopods, 126 : the 

 Gasteropods, 126 132: the lanthina, 132 134: the Litiopa, 134 : 

 Bivalve Mollusca, 135 : Bivalvular Leapers, 136 : Bivalvular Swimmers, 

 137, 138 112 



LETTER IX. 



Burrowing and stationary Mollusca : arenacolous,139 141 : byssife- 

 rous, 141 145 : cemented and pedunculated, 145, 146 : stationary 

 Gasteropods, 146, 147 : the Patellae, 147, 148. . - . . 139 



LETTER X. 



Boring Mollusca and nest-builders : saxicavous Mollusca, 149, 150 : 

 their mode of operation by boring, 151 : by a solvent, 151, 152 : Mr. 

 Osier's theory, 152 157 : Mr. Garner's theory, 157 : Mr. Hancock's 

 discoveries and theory, 157 162 : saxicavous Gasteropods, 162 : snails 

 are doubtful borers, 162 164: nest-builders and carriers, 164 166: 

 classification of Mollusca from differences in their power of locomotion, 

 167. . 149 



LETTER XI. 



Their system of aqueducts : variation of size in the same individual, 

 168, 169 : how produced, 169 171 : description of the aquiferous 

 system, 171174. .- ; . 168 



