35 



Brechites to Aspen/Mum. The description, it must be owned, is entirely inade- 

 quate ; still, we have but little doubt that it was intended for this shell. 



It is the aim of this paper to enumerate and deliue the various genera and 

 3pecies of Gastkocii.kn'id.k, giving their synonymy in full, and also their dis- 

 tinctive characters. In the progress of the work, difficulties have been en- 

 countered that were scarcely imagined at the outset. The older writers have 

 given as generally utterly inadequate descriptions, and have also in some cases 

 confounded two or more species under one name and description, — e. g. in 

 Oastroehaena cunaformis and A&pergillum Javanum. 



Then, again, many of the later species are founded on single or few speci- 

 mens, and characterized principally by variations of surface and ornamenta- 

 tion, which may be found to be permanent when a larger number of specimens 

 become known to us, but are most probably the result of accident, in a family 

 acknowledged to be peculiarly subject to distortion from external causes. 

 That a large number of these species could not be retained on present data, 

 early became apparent ; but the question with what forms they were to be 

 united has sometimes proved a perplexing one. Where we have merged two 

 or more species into one, our reasons are always stated ; but they must be 

 understood as mere opinions which future discoveries may very seriously 

 modify. 



Whilst the course we have thought proper to pursue may have resulted in 

 the suppression of some good species, it offers us, in those which have been 

 adopted as valid, objects distinguished from each other by well founded and 

 permanent characters. Unusual care has been taken with the synonymy of 

 the older species, the descriptions having been patiently studied out and com- 

 pared, and it is probable that the most of them have been assigned to their 

 true position ; but for reasons already alluded to, there can be no certainty 

 regarding this, and perhaps this paper should rather be regarded as a contri- 

 bution of facts and authorities as materiel for the future monographist, than 

 as an addition to positive knowledge. 



It will be found by reference to the succeeding pages that we have placed 

 in the synonymy of a number of genera and species many well known and 

 generally received names. To explain our motive for so doing, we deem it 

 important to enunciate the following general principle : 



We hold that the oldest generic name, accompanied by a sufficiently accu- 

 rate description for the purposes of identification, should always have priority ; 

 and the same rule applies to specific names: but in order to save naturalists 

 from the labor of consulting the writings of the ancients and the danger of 

 adopting a false application of their generally obscure descriptions, no pre- 

 Linnaean names should be used. 



The name of the naturalist who first describes a species of shell should for- 

 ever remain attached to the specific name, of which, for all the purposes of 

 memorizing or identification, it is properly a part ; and should our better 

 acquaintance with its structure and relations to other mollusea authorize its 

 removal to another genus from that in which it was originally placed by its 

 discoverer, then the latter's name should be followed by the word li Species," 

 to indicate the fact. 



Reference to Authors quoted. 



Adams, Arthur Description of Aspergillum Strangei, Proc. Zool. Soc. 



Lond. p. 91, 1852. 

 Adams, H. and A Genera of Recent Mollusea, ii. p. 334 (1856,) and 



p. 649 (1858.) 



Anton Verzeich der Conchylien, 1839. 



Argenville Conchyliologie, 1st edit. 1742; 2d edit. 1757. 



Beau Catalogue des Coquilles du G-uadaloupe. 1858. 



Bellevue, Fleuriaude Journal de Physique, liv. 1802. 



Blainville Manuel de Malacologie, 1825. 



