INTRODUCTION. XXI1 
the course of the work. ‘These plates are also intended to 
exhibit the leading principles of generic distinction, in a regu- 
lar series; as a reference to the *‘ Types of the Genera” (here- 
after given) will demonstrate. 
Let me here mention, that the Nomenclature of Colours 
-adopted in the present work, is that of WERNER, as exhibited 
and improved by Mr Syme of Edinburgh, in a work which 
ought to be in the hands of every Amateur of Natural His- 
tory. 
