CONTENTS. 



LETTER IV. 



PAGE 



The pearl Oyster, 49 : Pearls, their estimation and value amongst 

 the Romans, 49 52 : ancient Pearl fisheries, 52 : Pearl fishery of 

 Ceylon, 53, 54 : of the Red Sea, 54 : of Britain, 5458 : of America, 

 58 62. Shells worn as ornaments, 62, 63 : economical use of shells, 

 63, 64 : models for utensils and ornaments, 65, 66 : used in religious 

 services, 66, 67 : pilgrim shells, 67, 68. The Pinna, 68 : its silk, 68, 

 69 : the Tyrian purple, 6972 : the dye of the Whelk, 7274 : the 

 Tyrian purple, 74, 75 : China-ink, 76 : Mother-of-pearl, 76, 77 : 

 medicinal Mollusca, 77 : their vulgar uses, 77, 78 : their superstitious 

 applications, 79, 80. . . . . . . .49 



LETTER V. 



The use of the dead shell to other animals, 81 : the Hermit Lobster, 

 82, 83 : the Spider, 83, 84 : the Siphunculus, 84 : insects and worms, 84 : 

 the Nautilus, 8486. . . . . .81 



LETTER VI. 



The Mollusca in their relations to dead matter : the Teredo, 87 : 

 saxicavous Mollusca, 88, 89 : the origin of lime, 8991 : the creation 

 and succession of the Mollusca, 91 94 : tertiary formations, 94 : recent 

 formations, 94 96 : checks to the increase of Mollusca, 97 98. . 87 



'LETTER VII. 



An exposition of Cuvier's arrangement of the Mollusca : the cha- 

 racter of Mollusca, 100, 101 : their classes ; viz., Ccphalopods, 101 : 

 Pteropods, 101 : Gasteropods, 101 : Acephalcs, 101, 102: Brachiopods, 

 102 : Cephalopods, order and families, 102, 103 : Pteropods, their 

 genera, 104: Gasteropods, their orders, 104: Pulmones, 105: Nudi- 

 branches, 105 : Inferobranches, 105, 106 : Tcctibranches, 106 : Hetc- 



