18 Dr. Maton’s and Mr. Racxert’s 
tered, and we have ventured to state those reasons in the proper 
places. With regard: to- some of the terms employed by Lin- 
nus (especially in the description of the genus Venus) altera- 
tions seem necessary, on the grounds adverted to at some length 
in a former paper *. : 
In the synonyms, and references, it has been our most sedu- 
lous endeavour not to. mislead, either by transcribing upon trust 
from other authors, or by quoting such as are ambiguous, or im- 
perfect. The excellent descriptions. given by Linnzus, in his 
Museum Ludovice Ulrice Regine, we have, in most instances, ex~ 
tracted entire; and these extracts, it is hoped, will be the more 
useful, as that work, on account of its scarcity, cannot very 
generally be had recourse to, in England. We have also availed 
ourselves of the concise, but illustrative observations, given by 
.the same author in his Fauna Suecica and Systema Nature. 
Wherever such helps have failed us, we have subjoined to the 
essential characte: of each species short descriptions of our own, 
the ordinary size of the shell at its full 
period of growth (in the British Islands), as one of the most 
ready guidances towards identifying a specimen under examina- 
tion. It was one wish to have investigated, with our own eyes; 
some instances “this was not practicable, and, under duck cir- 
cumstances, we have contented ourselvés with adducing the most 
respectable authorities. To have omitted a species asserted to 
be British by writers of repute, merely because we had not been 
so fortunate as to haye seen pacen ourselves, would have in- 
dicated a very unb ecoming degree of suspiciousness ; and it 
would also ie been inconsistent with the Seige of this npe 
x Linn. Trans, vol. vi. p. 181. 
whieh 
SEE ieee Sa nes A 
NOVO E ee SP 
RAIN ace hae dE 
| 
3 
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