IV INTRODUCTION. 



the testaceous layer alternates, does not appear 

 the external substance; but this Epidermis is no 

 thin and brittle ; and soon disappears under 

 the friction to which most shell fish are exposed.* 



In the opinion of physiologists then, a shell is 

 regarded as simply a portion, the external 

 skeleton, of an animal ; and the generic character 

 of the molluscous inhabitant is estimated by 

 the preponderance of its various parts. 



In forming an arrangement designed to em- 

 brace the natural affinities, this is indeed the only 

 method which can be adopted. That of Lamarck 

 is entirely built on it ; and as the classification 

 of this eminent Naturalist is now chiefly followed 

 in England : the shells of the British Museum 

 being arranged by it, as well as the small col- 

 lection presented to the Museum of the Royal 

 Institution of Cornwall by the kindness of Sir 

 Charles Lemon, Bart., MP., it is judged proper 

 that the present work, and the classification of 

 the native specimens deposited in the Museum 

 at Truro in illustration of it, should not form a 

 departure from it. 



Yet it must not be concealed that there are 

 some things in the arrangement of Lamarck, 

 which display an imperfection that will probably 

 one day be fatal to it ; and one especially, which 

 it is surprizing should ever have been tolerated. 

 For however convenient it may be to the phi- 

 losophic student to begin his enquiries with the 

 lowest forms, and in the examination to travel 

 upward to the more complicated organization; 

 yet having attained his results, it will scarcely 

 be judged consistent with nature, to give those 

 lower forms a permanent place at the head of 

 the table. Man, rather than the Monad, should 

 be at the head of Creation. 



* Cuvier's Animal Kingdom, 



