Vi. PREFACE 
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 albocineta.* 
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 ef 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 chionea of Menke is chosen, being applicable 
to the whole species, of which D. squalida, Sby., D. biradiata, 
Gray, D. chione Sby. (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 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, Gld. signifies that it is 
uncertain whether the Bulla belongs to Gould’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 
in another of the sectional groups. Vide Brit. Assoc. Rep. Joe. cit. 
