BRITISH MARINE TESTACEOUS MOLLUSCA. 



CLASSIFICATION. 



IT will be convenient, with reference to this work on the 

 British Marine Testaceous Mollusca*, that a synopsis of the 

 classification of the whole tribe should be submitted, accom- 

 panied by a short analysis, that the incidents and position 

 of any particular family may at once be examined. Most 

 naturalists have their own plan of distribution with respect to 

 natural order ; perhaps, then, I shall not incur the imputation 

 of an unmeasured presumption, if I venture to offer a sketch 

 of mine, founded on forty years' sedulous investigation of our 

 indigena. I have not the vanity to suppose that my scheme 

 is superior to the methods of my brethren ; but it is novel, 

 and exhibits, as I think, a progressive advancement of animal 

 organization and harmony of arrangement from the beginning 

 of the class to its termination, by which groups of similar 

 affinities are insensibly united as far as is possible, and suc- 

 ceed each other, on the basis of external and internal anato- 

 mical considerations. 



These memoirs are the result of numerous visits to the 



* The main object of this work is the description of the animals of the 

 British marine testaceous Mollusca, and though a few of the freshwater 

 and land families and genera are mentioned, it is only incidentally, and to 

 fill up the outline of the British classification, but no account of their 

 species will be given. 



B 



