ON MOLLUSCA. 249 
place for the insertion of a few general observations on the 
principles of CONCHOLOGY, inasmuch as the naked and co- 
quillaceous do not form two distinct divisions, and that such 
general observations (which by the way involve all the in- 
terest in the subject to all except professed conchologists,) 
could with no propriety be introduced and distributed among 
any subsequent remarks we may have to make on the orders 
or genera. 
Conchology is the art of arranging the shells, or rather the 
protecting bodies of testaceous animals, so as to enable us to 
recognize them promptly and certainly, without giving any 
attention to the animals which they have contained, or con- 
tain, or at least regarding this part as a matter of very minor 
importance. We have already said quite sufficient concern- 
ing the animal, and concerning the shell too, as a portion of 
that living animal; what we have now to say will refer 
merely to the envelopes themselves, which may be preserved 
independently of the animal, and which, in fact, may have 
belonged to animals of classes and even of types very different 
from each other; and consequently in this point of view we 
must follow the method of Linnzus and of a great number of 
other naturalists, though we cannot avoid regarding it as 
totally artificial. 
For a long time this portion of natural history, which may 
almost be said to have been invented for the gratification of 
amateurs of the rare and brilliant, was regarded as a study 
nearly idle and useless by all true zoologists; and this was so 
far true that it was often more necessary to be acquainted 
with the shells in their artificial state, to which they were 
brought by the application of emery and other substances, 
and by processes which removed even one or two of their 
strata, than in their truly natural state, in which they were 
often rejected. , Consequently, all those shells which either 
naturally, or by art, presented nothing remarkable, no singu- 
