Descriptive Catalogue of the British Testacea. 19 
which is to lay before the student a descriptive catalogue of all 
our British Testacea. Such notices as are not indispensably ne- 
cessary to the discrimination of a species, or relate to what may 
be called its history, we have usually given in English; and it 
may here be remarked, that we have been particularly attentive 
to point out the discoverer, or first describer, of every shell > 
(wherever it was possible to arrive at certainty), retaining the 
trivial name originally attached to it, in preference to any other, 
provided it was not pre-occupied, or at variance with the specific 
characters, or with the Linnean principles of nomenclature. 
Had naturalists in general been more strict in this respect, and 
less fond of novelty of denomination, the science would have 
been much less confused in every department, than it is at pre- 
sent. The use of trivial names in natural history certainly does 
not consist in their being descriptive of the subjects to which 
they are annexed, but in their being permanent designations, 
which, as discovery seems to have no limits, the more arbitrary 
they may be, the better perhaps they will answer the purpose 
for which they are calculated. | 
Every person must be fully aware of the great utility of 
figures, as auxiliaries of description, which sometimes, from 
the nicety of the variations of subjects, cannot possibly be 
rendered all-sufficient for the student's instruction. Fortunately 
we have been preceded by many British iestaccolbgiMln whose 
works. in this respect afford very: ample. advantages; but where- 
ever a. figure was wanting, (ona 2 » ‘had fallen under 
our notice,) or wh € 8 t had been given were 
‘grossly incorrect, we have période to remedy the defect, by 
referring to engravings annexed to this paper. We judged it 
would be useful also, on some occasions, to figure closely-allied 
p2 I b.c Apocies 
