vu PREFACE. 
our deeper and less explored waters. Whether these in- 
clusions are justifiable or not, due care has been taken that 
no mistake can arise either in respect of the species referred 
to above, or of others found in-a similar condition, as it is 
noted under each species—unless such as are palpably 
common—whether it has been met with in a live or dead 
condition. 
A frequent source of vitiation in many lists exists in the 
importation of alien species in ballast. From this we are 
happily free, or nearly so; as no ballast is permitted to be 
thrown into the sea by vessels entering our ports, and 
stringent regulations on this subject have been in force for 
many years. It is still probable that at times such vitiation 
may occur, but the notes as to the living or dead condition 
of the species catalogued afford a safeguard against error 
arising from such a cause.* 
Under each species there has been added a short note on 
its British distribution, for information on which point I 
have to acknowledge my indebtedness to the works of 
Messrs. Forbes and Hanley, and J. G. Jeffreys, and to 
the various papers and local lists by Messrs. Alder, Forbes, 
Laskey, Leckenby and Marshall, M‘Intosh, Robertson and 
Brady, and others, scattered through many periodicals, and 
also to the dredging reports published by the British 
Association in its annual volumes. <A few foreign localities 
in which our Clyde shells have been found are also recorded; 
these are partly taken from private communications, but 
chiefly from the catalogues and notes published by Lovén, 
M‘Andrew, Dawson, Gould, Verkriizen, Jeffreys, and many 
others.t| Itis not pretended that an exhaustive list of such 
localities is here submitted, the books necessary for such 
research not being within my reach, but enough is given 
* Helix lactea, an inhabitant of the Mediterranean seaboard, was lately 
dredged off Skelmorlie, in the lawful possession of a hermit crab; and I 
found a specimen of Oliva ispidula on the shore at Carradale. 
+ The late Dr. P. P. Carpenter’s elaborate report on ‘‘The Mollusks of 
Western North America” (Washington, Dec., 1872), did not come into my 
hands in time to be made use of. It would appear from this revision of 
his former work that the matured judgment of its author led him to believe 
