INTRO MUCTION. qi 
edition of the ‘Systema’ has priority. With very few unre- 
corded exceptions, the whole of the shells enumerated in that 
edition were characterised from examples in our author’s private 
collection, as appears from the list appended to his interleaved 
copy of that publication. Hence, whenever a marked specimen 
is found in his cabinet, it may, provided, as is usually the case, 
it correspond to its description in the ‘ Systema,’ be fearlessly 
regarded as the type, more especially should the adjudication 
coincide with the general opinion of former conchologists ; for 
in all cases, where the balance of testimony is nearly even, I 
would yield to the popular opinion, not alone from a desire of 
avoiding all unnecessary changes of nomenclature, but because 
it is far from improbable that even as the collectors of the pre- 
sent age are wont to identify their specimens by comparing 
them with those in the typical collections, so, in the earlier 
period of conchology, the cabinet now alas! so confused in its 
arrangement was once the fruitful source of a like determina- 
tion of species: hence the opinions of the older conchologists 
descend to us with all the force of tradition. 
Three interleaved copies of the ‘Systema Nature,’ in the 
library of the Linnean Society, have afforded assistance in elu- 
cidating the more ambiguous species, and in strengthening one’s 
convictions upon those more clearly determined. The manu- 
script notes to the tenth edition were evidently the basis for the 
changes in the subsequent publication, and prove occasionally 
useful for the correction of typographical blunders, as well as 
explanatory of the less clear passages in the description of the 
additional species which were finally introduced, the intended 
diagnosis being often couched in different words, though with 
the same meaning. Far more important, however, is that copy 
of the twelfth edition which was corrected and enlarged by 
Linneeus for his projected thirteenth edition. The first volume 
of Martini’s ‘ Conchylien Cabinet,’ besides other copiously il- 
lustrated works upon Zoology, having been published previous 
to our author’s death, though posterior to his ‘ Magnum Opus,’ 
have enabled him to augment his previously scanty references 
to accurate delineations ; and these additional synonyms prove 
frequently decisive, where doubt previously existed, of the spe- 
cies actually designed by the great founder of systematic 
zoology. The third copy was the one possessed (ed. 12) by the 
