INTRODUCTION. 3 
admixture has not merely augmented to an almost inconceivable 
degree the difficulties of investigation, but has too frequently 
proved fatal to any accurate decision. Nevertheless, much 
valuable information may be gleaned from a diligent study of 
this collection. 
The original specimens, when large enough to permit it, had 
been inscribed by Linneus either with their names or with nu- 
merals corresponding to their position in his ‘ Systema;’ the 
smaller ones had been deposited in tin boxes, marked in a like 
manner; oftentimes, indeed, the numerals were written on both 
shells and boxes. It is worthy of remark, that these numerals 
more frequently corresponded to the series of the tenth than of 
the twelfth edition, a fair ground for believing that these shells 
were not merely his erroneous after-impressions of his own 
species, but were admitted and recognised types when the final 
edition was printed. 
In the determination of species, we may hold the marked 
shells to be conclusive testimony, whenever they accord with 
the published descriptions; sometimes, however, two shells (or 
boxes) may be found with a like set of cyphers, a casualty re- 
sulting either from the different numerical location of species 
in the two principal editions of the ‘ Systema,’ or from regarding 
distinctions as varietal, which the nicer discrimination of mo- 
dern science has proved to be essential. In the former event 
no practical difficulty can occur, as the shells, for the most part, 
belong to different genera, and are utterly dissimilar; in the 
latter case, that individual must be reputed the type which cor- 
responds more accurately with the description and synonymy. 
The authority of the unmarked specimens in the marked tin 
boxes is less constant. The carelessness of some hasty exa- 
miner has occasionally misplaced an example (a source of error 
averted in more recent times by the discipline of the Society, 
which requires the presence of the curator during each in- 
spection of the drawers): the intruder, however, may be readily 
detected, by a careful comparison of the entire contents of the 
case with the several descriptions of the indicated species in 
the various works of our author. The ink, too, has faded or 
become partially obliterated from many of both specimens and 
boxes. Should it prove possible, however, to decypher two, or 
even one (if it be the final one), of the three original numerals, 
