MOLLUSCA. 33 



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 Linncean 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 yett- 

 cribus Argonauta et Nautilus ad Naturam Picia et De- 

 scripta, Vienna, 1798. It is the joint production of L. A. 

 Fichel and J. P. C. A. Moll, and merits an attentive perusal. 



We a"re 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 of 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. 



SECT. II. Systems constructed from Circumstances con- 

 nected with the Habits of the Animal. 



The authors of the preceding class have laboured to bring 



