26 [Senate 



thougli now as numerous and diversified |n recorded forms as were 

 many of the Linnsean genera in the days of Lamarck, I have freely 

 adopted many of the generic names recently proposed, and have 

 even, in some few cases, added to them. It is a matter of secondary 

 importance, whether an accurately defined group takes rank as a 

 mere section in a subgenus, or as a leading division in a family ; but 

 the binomial designation is much easier for reference, than that by 

 sections. For ordinary purposes, it may be sufficient to cite the lower 

 division, the genus (like the family, etc.) being implied. When the 

 genus is required, it should have been always quoted, as it is in the 

 later sheets, thus : (Terehra) Myurella alhocincta*. 



In naming the genera and species, I have almost always followed 

 (to the best of my knoAvledge) the law of priority, with the modifi- 

 cations authorized in the Brit. Assoc. Rep. 1842, pp. 109 et seq. In 

 a few cases, however, in which different forms have been described 

 as distinct species, which I have thought it necessary to unite, I 

 have chosen that name (irrespective of priority) which represents 

 the typical state of the species. By this means, those who are not 

 satisfied with. the union can keep the accustomed nam6s for those 

 forms which they regard as distinct, without adding to the confusion. 

 Thus the name Dione chionaa of Menke is chosen, being applicable 

 to the whole species, of which D. squalida (Sowerby), D. hiradiata 

 (Gray), D. chione (Sowerby, pars), and perhaps D. elegans (Koch), 

 had been previously described from peculiar forms. 



To have dispensed with no fewer than 104 species constituted by 

 naturalists of reputation (exclusive of synonyms), and at the same 

 time burdened science with the names of 222 new ones, in a list 

 numbering not quite 700 species, may seem extremely presumptuous 

 in so inexperienced an author; as also may the opinions freely 

 expressed on various recorded statements. But fresh sources of in- 

 formation must always be expected to modify judgments formed 

 from insufi&cient materials; and, as a naturalist should desire truth 

 above all things, and wish to save others the necessity of wading 

 through the same labyrinth of errors from which he has with dif- 

 ficulty extricated himself, it appears a duty to lose no opportunity 

 of correcting those statements in previous works which are liable to 

 create confusion. The first person has been frequently used to show 

 that the statement put forth is not necessarily a fact, but simply 



* It would save mucli confusion, if those who divide genera would always make the subordinate 

 names of the same gender with the original genus ; also if authors, in describing new species in 

 old genera, the modern divisions of which are not generally recognized, would avoid repeating a 

 name already given in another of the sectional groups. Vide Brit. Assoc. Reports, loc. cit. 



