210 Mr. Brooke on Conchology regarded as a Science. 
destitute of shells. And as Pholas, Solen, Mya, Mactra, are some of 
his genera of shells, he evidently adopts the Linnean principle of esta- 
blishing a classification and nomenclature of shells distinct from, and in- 
dependent of, that of the animal inhabitants. 
In 1822 a work was published by the Rev. Dr. Fleming, entitled, 
“« The Philosophy of Zoology, or a General View of the Structure, Func- 
tions, and Classification of Animals.” And in 1828 the Ist volume 
appeared of ‘ a History of British Animals,’’ by the same author, exhi- 
biting a systematical arrangement of their genera and species. 
At page 406 of the first of these works, Dr. Fleming says, ‘the cha~ 
“* vacters furnished by the skin and its appendices are extensively em- 
<* ployed in the systematical arrangement of molluscous animals. Nearly 
** all those characters which distinguish the species, and many of those 
** on which genera are established, are derived from the form of the shell, 
*« the tentacula, or the colour.” If this be really so, that the form of 
the shell may supply both the generic and specific characters of the ani- 
mal, the study of shells alone becomes even more important than it has 
been already supposed. It will, however, appear afterwards that the 
very reverse of this process is recommended in a later work. 
The subject is again adverted to by Dr. Fleming, at page 430 of the 
same volume, where he says, ‘ enough is known of the animals of Spi- 
‘* rula and Nautilus to furnish some hints for those who are fond of elassi- 
*¢ fying animals from their analogies.” A passage which seems to imply 
dissent on the part of the author from the method of classing these ani- 
mals from their analogies rather than from their shells ; a dissent, how- 
ever, from the only principle upon which, it would appear, a correct 
classification of animals can be established. 
It is from this conflict of first principles, and the practical conse- 
quences to which it has given rise, that the ambiguity and uncertainty 
are produced which meet the conchological student at every stage of his 
enquiry. If, for example, he turns to the division Cochleade of Dr. 
Fleming’s British Animals, (page 255,) he observes that the first genus is 
named Cyclostoma, and which hence would appear to beananimal. But 
he has perhaps seen a shell so named, and he is therefore at a loss to know 
whether the term Cyclostoma implies an animal or a shell. To satisfy 
his doubts he turns to the description of this genus, and he there finds 
