212 Mr. Brooke on Conchology regarded as a Science. 
yet a few lines further on, he has the expression, ‘* The shedls which 
** form this genus,’ &c. Is, it may be asked, Melanopsis an animal 
ora shell, or both ? and is not the name derived from the shell ? 
Under Catophragmus Mr. Sowerby alludes to ‘ correct first princi- 
ples’”’—he, however, states that these “‘ are only to be obtained by 
* the study of the Mollusca which form and inhabit shells,” ** yet (he 
* says) the shells themselves may in most cases be regarded as indicating 
*¢ many of the more important facts in connection with the history of 
“ 
ec 
n 
their animal inhabitants, and may consequently be generally consi- 
* dered as sufficient to demonstrate characters strong enough for the 
establishment of genera.’’ But genera of what ? animals or shells ? 
If of animals, they do not properly belong to Mr. Sowerby’s work on 
shells, and if of shells, the passage means no more than that genera of 
shells may be established upon the characters of shells alone. The re- 
mark that genera of animals form no part of Mr. Sowerby’s work is 
strongly enforced by himself, under the genus Dentalium, where he says, 
“* whatever may be the nature of their animals, we are engaged to give 
© an account of shells alone.” And the genus /nostoma affords an in- 
stance of the establishment of a new genus from the form of the shell 
alone, where the animal is supposed to resemble that of Helix. The 
consequence of thinking about animals while writing about shells, is the 
occasional production of observations which could not otherwise have 
been made; as, for example, the quotation from Lamarck, under the 
genus Cassis, “ that the shel/s live in the sea ata distance from the 
«© shores, and upon sandy bottoms, where they bury themselves in the 
«« sand.” And under Achatina Mr. Sowerby speaks of shells of differ- 
ent characters and habits. 
It is not obvious what is intended to be implied by the phrase habits 
of shells, if it be not their colours and their epidermis, (the latter of 
which, it may be observed, is frequently a very loose habit,) unless in- 
deed the practice of burying themselves be termed a habit, to which we 
are perhaps indebted for the preservation of the numerous fossil speci- 
mens that now exist, and which may be conceived to have formerly prac- 
tised self-interment more or less profoundly, in all the then subjacent 
beds of seas and lakes. 
A similar want of precision in the use of terms connected with this 
“ec 
