102 ANALYTICAL INDEX. 



CHAPTER II. THE TESTACEA, . PAGE 15 



Particular classes of beings protected, and others exposed, ib. 



Weapons of offence and defence, 

 Process of incrustation, . 



The shell progressively consolidated, . 1 ? 



Great variety in the form and matter of the shells, ib. 



Shell animals chiefly related to the Limax, . ]1 >- 



Animals pertaining to the Crustacea, the Amphitrite, the Limax, the 



Ascidia, and the Tethys, 

 Little uniformity among them, . 

 Naturalists perplexed with such as the tenant of the Dentalium and 



the Chiton, ... >b. 



Univalve Testacea in the Scotish waters not uncommon, ib. 



The bivalves extremely rare, 



Few bivalves belong to the fresh waters, . >b. 



Shell not the distinction of genera, 



Precise position and arrangement of shells not yet agreed, 

 Testacea the univalves and bivalves, 



Traffic in shells their form and colour, il>. 



Discovery of their precise figure difficult, 



SECTION I. UNIVALVES, ... ib. 



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

 Shell generally designed for protection, . . b. 



1. SIGARETUS, ..... 



Sigaretus an animal between the Limax and Testacc.a, ib. 



Its form, proportions, and appearance, . ib. 



Swims supine, .... 'b. 

 Colour mostly grey, . 



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



The Sigaretus is not common, . ib. 



Plate V. described, ... ib. 



CHITON The Boat Shell, . . 24 

 A univalve shell, inhabited in nearly all cnses, 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, . . . i!5 



