Ixxxii INTRODUCTION. [CH. 



lusca in the European seas, many theories have been 

 from time to time advanced, each of which would divide 

 this great area into several distinct parts, or what are 

 called " provinces." Professor Milne-Edwards, in the 

 'Annales des Sciences Naturelles' for 1838, proposed 

 the following division 1. Scandinavian, 2. Celtic, 3. 

 Mediterranean. Mr. S. P. Woodward, in his very useful 

 little treatise, entitled l Manual of the Mollusca' (the 

 last edition of which was published in 1856), considered 

 that there are four provinces, viz. 1. Arctic, 2. Boreal, 

 3. Celtic, 4. Lusitanian ; and these, according to this 

 writer, were "framed upon the widest possible basis." 

 In a posthumous work of the late Professor Edward 

 Forbes, which was most ably continued and edited by 

 Mr. Godwin- Austen in 1859, under the title of 'The 

 Natural History of the European Seas,' a fifth province 

 (the " Mediteranean ") has been added to those above 

 enumerated. The latter scheme of distribution has been 

 recently adopted by Mr. M* Andrew in the ' Annals of 

 Natural History ' for December 1861. 



Now, although such a division into "provinces" or 

 separate areas of distribution is very plausible, and pos- 

 sibly may be maintainable in the same sense as the divi- 

 sion of Mankind into distinct races, a definite principle 

 seems to be wanting in their construction. If we com- 

 pare any one of these schemes with another, a very 

 material discrepancy is observable as to the relative 

 limits of the provinces. For instance (not to travel far 

 from home), Milne-Edwards considered that the Celtic 

 province had its southern boundary in the Straits of 

 Gibraltar ; Woodward restricted the same limit of this 

 province to our own coasts ; while Forbes advocated its 

 extension "from the Bay of Biscay to the Baltic Sea." 



The principle of definition, as well as of construction, 



