PRELIMINARY REMARKS. Vv 
on this subject, see a paper in the Proceedings of the Boston 
Society of Natural History, Nov. 1851. 
In citing authorities I have referred to the author who gave 
to the species the name which it now bears ; — the whole name, 
and not a part of it. I need only refer, as authority for so do- 
ing, to the names of Linneus, Cuvier, and Agassiz. The 
practice of citing the author who gave the specific designation 
—a part of the name — is an innovation, which has become 
frequent among Conchologists during the last thirty years. 
As the importance of an accurate knowledge of the distribu- 
tion of animals over the earth is now generally admitted, I have 
paid particular attention to the geographical and bathymetrical, 
or horizontal and vertical range of each species on our coast. 
To indicate the vertical range, I have used the terms applied to 
the zones of the sea by Professor Forbes, viz. : — 
Littoral, the space between high and low water marks. 
Laminarian, from low water mark to fifteen fathoms. 
Coralline, from fifteen to fifty fathoms. 
Deep Sea Coral, from fifty to one hundred fathoms and over. 
Many of our species have been hitherto obtained only from 
the stomachs of the ground-feeding fishes, and therefore their 
true localities, and the depths at which they live, have remained 
unknown. The notes of dredging excursions furnished me by 
my friends, and my own operations, have enabled me in most 
cases to give these localities and depths with accuracy ; and 
wherever they are mentioned, they are those at which the spe- 
cies has been taken with the dredge. As authority for these lo- 
calities | have referred to the gentlemen by whom they were 
