4 INTRODUCTION. 
the erased numeral or numerals may generally be deduced ; for 
knowing, from the simple fact of its having been written on, 
that the object (be it box or specimen) is typical or type- 
containing, we are enabled, by determining the generic position 
of the example in the Linnean arrangement, to so greatly 
reduce the limits of according numbers, that what with certain 
of the species having been clearly ascertained, and what with 
the specified characters of others being utterly dissimilar, the 
possibilities will rest between two or three at the utmost, and a 
final decision may be accurately arrived at through a comparison 
of the specimen with the descriptions and figures of this small 
remainder: for although the Linnean diagnoses are indisputably 
too brief to distinguish a shell from subsequently discovered 
allied congeners, their antithetical style was especially framed 
(and is admirably adapted) to separate the few known species of 
the ‘Systema’ from each other.* 
Were all the shells thus comparatively easy of identification, 
a few months’ labour would have sufficed for the scrutiny: but, 
unfortunately, all traces of writing have disappeared from one- 
half at least of both boxes and specimens. One method, and 
a right wearisome one, alone remained. Linneus has left us a 
catalogue of his shells, and we know that the species in his list 
(a very full one) are all distributed in one or other of the 
drawers of his cabinets. On carefully comparing the descrip- 
tion of any sought-for species with every specimen in his col- 
lection, we shall rarely, if ever, find more than half-a-dozen 
whose characters will at all approach the brief essentials of the 
definition. Of these six, two alone will perchance be repre- 
sented by the figures cited in the synonymy, and probably one 
alone will agree with both figures and description. In such an 
event, we may fairly regard that individual as the lost type, in- 
asmuch as it is the sole shell in the entire collection which 
* To illustrate our meaning more plainly, let us imagine an extreme case. 
Suppose upon an Helix ericetorum we descried a central 8, with vestiges of an 
unknown figure on either side of it. Of the numerals from 1 to 7, by which 
that 8 could have been preceded, the generic characters of the shell exclude all 
but 6; of the ten cyphers which may follow, 0, 1, 2, 8, 9 pertain to species al- 
ready determined: the great magnitude attributed to (68)4, the utterly dissimi- 
lar shapes to (68)5 and (68)7, and the narrow perforation to (68)6, forbid all 
thought of them: the characters of 683, on the contrary, most perfectly agree. 
