102 ANALYTICAL INDEX. 



CIIAITEU II.— THE TESTACEA, page l.-i 



Particular classes of beings protected, and otliers exposed, . il). 



Weapons of oflence and defence, . . . . 1 fi 



Process of incrustation, ...... il). 



The shell progressively consolidated, . . . 17 



Great variety in the form and matter of the shells, . . il). 



Shell animals chiefly related to the Lhnax, ... ib. 

 Animals ])ertaining to the Crustacea, the Amphitritc, the Liiiiax, the 



Ascidia, and the Tethys, .... IS 



Little uniformity among them, . . . . . ib. 

 Naturalists perplexed with such as the tenant of the Dentalium and 



the Chiton, ...... ib. 



Univalve Testaeea in the Scotish waters not uncommon, . ib. 



The bivalves extremely rare, . . . . . ib. 



Few bivalves belong to the fresh waters, . . . ib. 



Shell not the distinction of genera, .... ib. 



Precise position and arrangement of shells not yet agreed, . 1!) 

 Testaeea — the univalves and bivalves, . . . .2(1 



Traffic in shells — their form and colour, . . . ib. 

 Discovery of their precise figure difficult, . . .21 



SECTION I.— UNIVALVES, ib. 



In the field of creation Nature advances by slight transitions, ib. 



Shell generally designed for protection, . . ib. 



§ 1. SiGARETUS, ...... 22 



Sigaretus an animal between the Limax and Testaeea, ib. 



Its form, proportions, and appearance, . . ib. 



Swims supine, ..... ib. 



Colour mostly grey, . . . . .23 



No important distinction between the grey and the yellow, ib. 



The Sigaretus is not common, . . . ib. 



Plate V. described, .... ib. 



Chiton— T/;e Boat Shell, ... 24 

 A univalve shell, inhabited in nearly all cases, by the 



Limax species, . . . . . ib. 



Figure like an inverted boat, ... ib. 



Resembles the Patella, . . . . ib. 



Those on the Scotish shores small, . . ib. 



§ 1. Chiton fascicularis, . . . . ib. 



Description of shell, .... ib. 

 Animal brown — moves slow, . . .25 



