FAUNA OF THE CLYDE SEA-AEEA. 
465 
is the shallowest, being about 23 fathoms. In the case of some 
of the other basins, however, it is so far from marking out their 
limits that it does not touch the tops of the ridges which sepa- 
rate them. To Dr. Murray I owe the suggestion that it might 
be worth while to compare the faunas of the deepest parts of 
the basins, taking some other contour-line as the upper limit. 
I have therefore gone over the Table given above and selected 
from it those species which are found in proximity to the bottom 
of each basin. The depressions themselves vary so much in 
depth that I have thought it advisable to record both the forms 
w T hich are found below the 50-fathom ; line and (in a separate 
column) those which are found within, say, 5 to 20 fathoms 
of the bottom of each basin. Furthermore I have excluded 
those free-swimming forms whose distribution in regard to depth 
cannot be regarded as absolutely fixed. On this ground I have 
omitted the Fishes, Cephalopoda, Amphipoda, and part of the 
Macrurous Crustacea (viz. the genera Hippolyte, Pandalus , and 
their allies) ; the Polyzoa, Hydroida, and Sponges have also been 
neglected because they have been insufficiently studied. 
In the subjoined Table the following symbols have been 
used : — 
* = occurring at the depth mentioned in the head of the 
column. 
t = occurring in the locality, but at a depth less than those 
under consideration in the table. 
~W = Widely-spread species. 
N = Northern species. 
S = Southern species. 
