liv 
THE VOYAGE OF H.M.S. CHALLENGER. 
DISTRIBUTION. 
Though we are still without the data which would enable us to give a complete 
exposition of the distribution of the Hydroida, our knowledge of this has been very 
much extended by the explorations of the Challenger, and both in the horizontal 
distribution of these organisms, and in their bathymetrical range, important accessions 
have been made to it. 
With the view of giving as graphic an expression as possible to the distribution 
of the species obtained during the voyage, I have divided the whole track of the 
Challenger into the following sixteen Regions, named either from the adjacent lands 
or from their position in the great oceans through which the course of the expedi- 
tion lay. Their boundaries are detailed below and may be seen in the Map at the 
end of this Report. In order to render them as simple as possible, I have made the 
Regions to consist of rectangular areas, each limited to the north and south by parallels 
of latitude, and to the east and west by meridians of longitude. Their size varies much, 
and they are framed without regard to their occasionally encroaching on the adjacent 
continents. 
Though the species are very unequally distributed among the various Regions, it was 
only from two of these Regions, the Britanno-Gallic whose Hydroid Fauna has been 
already well investigated, and the Antarctic, that no Hydroids were brought home. 
I. Britanno-Gallic. 
Limits — Northern, lat. 51° N. 
Southern, lat. 45° N. 
Eastern, long. 0° 
Western, long. 20° W. 
It includes the south-western extremity 
of England, and the north-western and 
western coasts of France. 
II. The Azoric. 
Limits — Northern, lat. 45° N. 
Southern, lat. 35° N. 
Eastern, long, 5° W. 
Western, long. 50° W. 
It includes the Azores, the western coast 
of Spain, and Gibraltar. 
III. The Nova-Scotian. 
Limits — Northern, lat. 50° N. 
Southern, lat. 40° N. 
Eastern, long. 50° W. 
Western, long. 75° W. 
It includes Nova Scotia and the neigh- 
bouring coast of North America. 
IY. West Indian. 
Limits— Northern, lat. 40° N. 
Southern, lat. 10° N. 
Eastern, long. 50° W. 
Western, long. 80° W. 
It includes Bermuda, the West Indian 
Islands, and the northern coast of South 
America. 
