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. lhat 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., M.P., it is judged proper 
that the present work, and the classification ot 
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 oj 
the table. Man, rather than the Monad, should 
be at the head of Creation. 
* Cuvier’s Animal Kingdom. 
