INTRODUCTION. V 



Another objection will strike the mind of such 

 as may seek their occupation or amusement in 

 examining the more solid forms contained in the 

 Museum. As the modern classification arranges 

 in close connection the Molluscs which may pos- 

 sess or are deprived of, a testaceous covering, or 

 in which the shells, taken alone, may appear of 

 very different forms, a discordancy may appear 

 which shall seem far removed from our ideas of 

 relationship in nature. The natural affinities, 

 however, are more dependant on the soft than 

 the solid portions, although unhappily the art 

 has not yet been found, of preserving the latter 

 in a state fit for examination. In some instances 

 also, the shell alone is known to Naturalists : 

 the inhabitant never having fallen in the way of 

 an observer. But to obviate as much as possible 

 all the difficulty likely to be thus encountered ; 

 and more especially for the benefit of those who, 

 feeling an interest in the subject, may yet discover 

 the philosophic arrangement to be rather an hin- 

 drance than an assistance, an attempt is here 

 made to combine the spirit of the Linnean 

 method with the arrangement of Lamarck, on 

 which the work is founded. The manner of 

 acquiring information may, and frequently ought 

 to be, different from that in which it is retained ; 

 and Mr. Bicheno (Trans. Lin. Soc. vol. J 5,) has 

 shown how well fitted in this respect an artificial 

 method is, to lead to the more easy and perfect 

 acquisition of the natural. 



It is with a view to this, that a rough outline of 

 an arrangement is subjoined, by which it is hoped 

 the student will be assisted in his endeavour to 

 discover the place of a shell, the scientific name 

 of which may be unknown to him. The dis- 

 tinction of kindred species, however, can only 

 be made, by reference to good figures, combined 



