INTRODUCTION. 3 



that a knowledge of the one is indispensable to the 

 study and acquirement of the other ; as the former 

 assists in elucidating most satisfactorily many of the 

 phenomena of nature, and the extraordinary mutations 

 this planet has undergone; which, without it, would 

 have remained in a state of much greater obscurity. 



To the unwearied and immortal labours of Linnaeus 

 in forming his Systema Naturae, the world will for ever 

 remain greatly indebted; but, from the fallibility of hu- 

 man nature, the magnitude of the undertaking, the 

 greater diffusion of scientific research, and subsequent 

 discoveries, it has become absolutely necessary to make 

 such alterations in his system, (particularly in that part 

 of it which treats of the Testaceae), as will explain the 

 generic characters with greater precision, form a more 

 natural association of their species, and constitute new 

 genera of such as were unknown, or had escaped his 

 observation at that period; the propriety of which it 

 may be presumed Linnaeus himself must have admit- 

 ted, had he existed at the present time. 



Many subsequent writers on Conchology, impressed 

 with this necessity, have suggested improvements, 

 and pointed out distinctions in the arrangement of the 

 b 2 



