CONCHOLOGY. 
shells known must be either excluded from 
the system, or be placed at hazard ; and of 
course without order or connection with 
those whose animals we are acquainted with. 
The latter are chiefly such as are confined 
to the coasts of the European seas, and 
some of the terrestrial and fresh water 
kinds, which, from their abundance and 
locality, have obtruded themselves upon 
the investigations of the naturalist. Even 
our knowledge of those is exceedingly im- 
perfect. 
The best characters, upon which to found 
all systems of natural history, must be those 
most obvious and accessible. All ranks ot 
animals, as nearly as can be wifli conve- 
nience, should be arrapged by apparent 
and external characters. While we study 
shells, without regarding the animal, we 
are aware they aie but considered par- 
tially. The animals that inhabit them 
should guide us in our researches ; they 
^lone are the fabricators of the shell, and 
the shell is only their habitation, to which 
they give the form, the bulk, hardness, 
colours, and all the peculiarities of ele- 
gance we admire. If we were to examine 
these new and almost unknown beings, we 
should discover a number ot parts as re- 
markable for their structure as their func- 
tions, and an infinite var iety of curious and 
interesting particulars relative to their ge- 
neral habits and manners of life. It is a 
subject worthy of the serious contemplation 
and attention of the naturalist, and should 
never be neglected when an opportunity 
offers. Butasystem ofconchology, founded 
entirely on the structure of the animals, 
must, probably, ever remain one of the 
desiderata of natural science. 
In the superficial arrangement taken from 
shells alone we are not exempt from diffi- 
culty. Shells vary exceedingly in form and 
colour in the different stages of their 
grow th, and in this case we should some- 
times derive niaterial assistance from our 
knowledge of the animal. Young shells 
have been described as specifically distinct 
from the parent or older shells by mqny 
writers. It indeed requires a greater de- 
gree of caution in determining tlie species, 
nay, even genera, of shells, in the different 
periods of growth, than may be imagined ; 
of this we could adduce many very remark- 
able instances, a few it may be necessary 
to mention, to guard the common observer 
from forming hasty and erroneous couclq- 
sions. 
Many of the cypraeae, or cowries, when 
young, have the appearance of a volute, 
the thick denticulated fold of the exterior 
lip being wholly wanting, and the column 
being only partially plaited as in the true 
voluta. The young of the alated shells, in 
general, are destitute of tliat broad expan- 
sive or furcated lip, called the wing, The 
spires in many of the turreted kinds ot 
shells, when young, are blunt ; obtuse, or 
terminated in a large globular head, ex- 
ceeding the size of the whorl beneath, but 
as the shell advances in growth, it developes 
itself, extending in a spirgl direfction, and 
thus in the old shells the number of spires 
is greater than in the young ones. The va- 
riations in the growth of the patella tribe 
are often so considerable, as to almost defy 
the critical observer to determine them. 
Still, however, the conchologist, by the dint 
of application and nice discrimination, will 
be at last enaWed to fi?^ on certain cha- 
racters peculiar to every species, and be, 
by that means, enabled to decide on the 
species of a shell under every stage of 
grpw'th. 
The primary character must be taken 
from tbe shell, becausq this we are acquaint- 
ed with, while the animal is oftentimes uq- 
kqowm to us. But the structure of tlie 
animal should be regarded in the construc- 
tion of genera, when it can be ascertained, 
as a secondary consideration to guide us in 
the formation of new genera, or in cor- 
recting the old, as opportunities qf investi- 
gating them occur. 
Slaving defined the meaning of a testa« 
ceous animal, and endeavoured to prove 
that the slnicture of the shell is the most 
material object to be regarded in a primary 
view, we shall proceed next to an elemen- 
tary elucidation of the several parts of which 
it is composed, 
In conchology, as in any other science, 
the student must necessarily acquire, in the 
first instance, a distinct knowledge of the 
terms employed. These, except such as 
relate to subordinate charactei's, or specifi- 
cal distinctions, and which require no ex- 
planation in this place, may be simplified 
and reduced to a small number. In the se- 
lection of these terms we can abide by no 
one particular authority : we must be gene, 
ral, deriving onr terms from various sources, 
or inventing new ones. Hitherto in treat- 
ing on the different articles of conchology, 
it has been our aim to adhere as nearly to 
the authority of Linnseus as possible. 
All shells or testaceous bodies hitherto 
discovered, may be dividod into three priu- 
