VI. PEEFACE 



it may be sufficient to cite the lower division, the genus (like 

 the family, &c.) being implied. "When the genus is required, 

 it should have been always quoted, as it is in the later sheets, 

 thus (Terebra) Myurella albocincta* 



In naming the genera and species, I have almost always 

 followed (to the best of my knowledge) the law of priority, 

 with the modifications 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 (irre- 

 spective 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 names for those forms which 

 they regard as distinct, without adding to the confusion. Thus 

 the name Dione chioncea of Menke is chosen, being applicable 

 to the whole species, of which D. squalida, Sby., D. Uradiata, 

 Gray, D. cliione Sby. (pars), and perhaps D. elegam, 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 

 game 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 information must always be expected to modify 

 judgments formed from insufficient materials : and, as a natu- 

 ralist 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 difficulty extricated himself ; it 

 appears a duty to lose no opportunity of correcting those state- 

 ments in previous works which are liable to create confusion. 

 The first person has been frequently used to shew that the 

 statement put forth is not necessarily a fact, but simply my 

 interpretation of a fact : and for a similar reason I have freely 

 employed the mark of uncertainty [?] , which is to be under- 

 stood as always referring to what follows, and not the word 

 going before. Thus Bulla ?nebulosa, Grid, signifies that it is 

 uncertain whether the Bulla belongs to Grould's species : while 

 ?Alaba conica signifies that the generic position of the species 

 conica is doubtful. 



* It would save much confusion if those wh:> 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, 

 n another of the sectional groups. Vide Brit. Assoc. Hep. loc, cit. 



