CONTENTS. XV 



PAGE 



on the animal, 411 : apex of bivalves, 411, 412: the hinge margin, 

 412: direction of the whorls, 412, 413 : dextral and sinistral bivalves, 

 413: equivalve and inequivalve shells, 413, 414 : irregular shells, 414 

 — 421 : variations on external surface, 421, 422 : variations in size, 

 423: colouring of shells, 423—425: structure of shells, 425—433: 

 crystalline structure, 426 : rhombic crystalline structure, 426—430 : 

 prismatic crystalline structure, 431 — 433 : Mollusca dissolve their 

 shells, 433—438 : how they bore rocks, &c, 438—440 : do not dis- 

 solve extraneous bodies, 440, 441 : the foot deposits shelly matter, 

 441, 442 : the operculum, 442 — 444 : the annular operculum, 444, 

 445: subannular opercula, 445— 447 : spiral opercula, 447— 456. . 408 



LETTER XXIV. 



Nomenclature of acephalous Mollusca : use of nomenclature, 457, 

 458 : terminology of the Tunicata, 458, 459 : cellulose, 459 : termino- 

 logy of bivalves, 459 : the Pholas and Tubicola?, 459, 460 : normal 

 bivalves, 460 — 469 : the ligament, 465 and 468 : terminology of the 

 Brachiopoda, 469—472. . . . . .457 



LETTER XXV. 



Terminology of multivalves, 473, 474 : of simple univalves, 475, 

 476: of spiral or turbinate univalves, 476—486: the Cypraea, 477, 

 478 : colours, 480 : sub-bivalves, 483 : the operculum, 483 — 485 : the 

 epiphragm, 485 : terminology of multilocular shells, 486 : terrestrial 

 or land shells, 487 : fluviatile and lacustrine shells, 488 : shells of 

 brackish water, 488 : littoral shells, 488 : sea-shells, 488 : dependency 

 of their colours on light, 489, 490 : importance of nomenclature, 

 490, 491 . . . . . • . .473 



LETTER XXVI. 



The History of Conchology : Aristotle, 492, 493: Pliny, 494 : Albertus 

 Magnus, Belon, &c, 495 : Fabius Columna, 496, 497 : origin of Muse- 

 ums, 497: Bonanni, 498—500: Lister, 500—503: Reaumur, 503, 

 504 : collectors and collections, 505, 506 : Walter Charlton, 507 : 

 Major, 507: Linnaeus, 508 — 510: Daubenton and Guettard, 510: 



