BUCCINUM. 169 



variation both in form and sculpture, and to obsolescence or ero- 

 sion of the surface-markings. The identification of imperfect or 

 worn specimens is extremely difficult in this genus.* The late 

 Dr. William Stimpson studied with great care the species of Buc- 

 cinum, having before him fine suites of specimens and possessing 

 a special experience in this genus which few of his successors 

 can claim to have enjoyed. I think it inadvisable, however, to 

 use his published researches as the skeleton of the present mono- 

 graph, subscribing to the doubt expressed by Dr. Jeffreys that 

 " Whether all those which he reckoned distinct will stand the 

 test of a more extensive examination of this extremely variable 

 group is questionable." During the fifteen years that have 

 elapsed since the publication of Stimpson 's researches, the num- 

 ber of nominal species has been largely increased, mainly through 

 the labors of W. H. Dall in Arctic Western America, of Yerkriizen 

 in the waters of Newfoundland, and of Sars and Friele in Nor- 

 way ; still, no monography of the genus subsequent to that of 

 Stimpson, has appeared. The earlier monographs by Reeve, 

 Kiister and Kiener contain, of course, heterogeneous assemblages 

 of species belonging to numerous genera and are therefore almost 

 utterly valueless for the purpose of comparison and classification 

 of the species. 



I annex the synoptical table of species given in connection 

 with Stimpson's monograph. 



Very few of the later species being known to me autoptically, 

 I fear that this portion of my work may be considered autosche- 

 diastical by some of my brother conchologists. 



The great variability of the species, a common characteristic 

 of Arctic mollusca, has caused almost every student of the Buc- 

 cinre, to estimate differently the range of variation permissable 

 within specific limits, so that what is referred to by one author 

 as B. undatum, for instance, may include less or more than the 

 specific form as herein limited, or as understood by all others ; 

 may include portions of related species, which thus become dis- 

 membered and themselves distributed among their allies or may 

 refer exclusively to forms herein characterized as distinct. 



* William Stimpson, in Canad. Nat. N. 8. II, 364. 1865. 

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