VI PREFACE. 



first appearance.* The conclusion will not be found dis- 

 figured by those gross typographical mistakes which per- 

 vade the earlier portion, errors too numerous for the author 

 to venture upon a list of " Errata." A correct printer 

 cannot be too highly appreciated by the writer upon natural 

 science ; the reputation of Linnseus has suffered from the 

 misprints of his synonymy. 



In the arrangement of the synonyms brevity alone was 

 originally aimed at (such a reference as " Ch. f. 399" was to 

 simply imply that Chemnitz had there figured the same 

 shell, not necessarily that he had similarly designated it), 

 Lamarck's names were usually placed first, and the vicious 

 principle adopted of ascribing species, not to their first 

 describer, but to the systematist who may have eventually 

 located them in the modern genus. After page 289 the 

 order of priority has been more attended to, and the 

 references to such writers as Lister, Knorr and Argenville, 

 who did not attach binomial epithets to their drawings, 

 have been inserted in brackets. 



The author's enlarged experience has enabled him, in- 

 deed, to discern these and many other blemishes in his 

 youthful work, but has, likewise, strengthened his con- 

 viction of the great utility of the condensation, portability 

 and suggestiveness which characterize it. The delicacy and 

 minute fidelity of Wood's engravings may, perchance, be 

 equalled, but cannot be surpassed. 



* Plates 20 to 24, with their explanatory text, were published on 

 the 26th of July last. 



