MOLLUSCA. So 
copica, 1789 and 1795, exhibited many figures of the mi- 
nute shells of Portoferrara, &c. Mr. Adams likewise de- 
scribed the minute species which he observed on the coast 
of Pembrokeshire, in the third and fifth volumes of the 
Transactions of the Linnean Society of London, and other 
species of British growth have been investigated by the au- 
thor of Testacea Britannica. We shall close this list with 
noticing the Testacea Microscopica aliaque minuta ex gen- 
eribus Argonauta et Nautilus ad Naturam Picta et De- 
seripta, Vienna, 1798. It is the joint production of L. A. 
Fichel and J. P. C. A. Moll, and merits an attentive perusal. 
We are aware that such microscopic investigations are 
regarded by some conchologists:as useless, so that the mi- 
nute species are excluded from their systems. But it is 
surely a strange method of proceeding in natural history, to 
judge of the merits or importance ef species from their size. 
It is true that we are still ignorant of the inhabitants of 
those shells, and may long continue to be so; but our pre- 
sent knowledge of these shells has enabled us to fill up many 
blanks, to perceive several new relations, and even to draw 
some important conclusions. 
That this sort of inquiry has in many instances been in- 
judiciously conducted, all who are acquainted with the sub- 
ject must admit. Due care has not been taken to distin- 
guish these minute testacea from the fry of the larger shells, 
so that the number of species has been very injudiciously 
multiplied. These remarks apply to several figures of 
Walker, and to a still greater number of those of Adams. 
Secor. Il—Systems constructed from Circumstances con- 
nected with the Habits of the Animal. 
The authors of the preceding class have laboured to bring 
