ii INTRODUCTION. 
naturalists have bestowed upon us. Nevertheless, much 
caution has been found requisite in altermg any of the re- 
corded habitats; since our knowledge of the precise limits of 
geographical distribution is somewhat hypothetical. 
To remedy the last objection alluded to, the Editor has 
carefully traced out the original figure from which the minia- 
ture one was taken (for almost all the engravings, excepting 
those of the Supplement, were copied from published draw- 
ings), and elaborated his synonymy (an original one) from 
the species there represented upon a larger scale. His re- 
ferences consequently apply to the figures, not to the Lin- 
nean names. The labour expended may in some degree be 
estimated by the long list of books referred to; a list which, 
independently of its necessity as explanatory of the abbre- 
viations, cannot be devoid of utility to the less advanced 
students of Conchological Bibliography. 
As the whole of the letterpress, except the first column, 
(Wood’s Linnean names) is entirely original, the writer should, 
perchance, have styled himself the Author, rather than the 
Editor; yet, as the text, in the present work, is avowedly 
subsidiary to the engravings, he has contented himself with 
the less honoured appellation. Although the portion alluded 
to, has been preserved to facilitate the finding of previous 
references to the ‘ Index,’ it must not be conceived, from its 
retention, that the names there specified are imvariably the 
first, or most desirable: the preferential specific epithets 
should be deduced rather from the last column, (in which 
they usually occur in the order of their publication) and 
from the dates mentioned in the list of ‘Abbreviations.’ 
The Appendix, which contains about 960 figures of species 
and genera not inserted in the original publication, is issued 
as a separate volume, the drawings being accompanied by a 
descriptive letter-press, expressly written to elucidate the 
bivalves delineated in the Index Testaceologieus. 
