192 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
(Fig. 36) is of comparatively little importance in oceanography, 
because so largely dependent on depth; but it can not be neglected 
because of the part it plays in the biology of the bottom fauna. South 
and west of Cape Cod the bottom salinity (leaving out of consideration 
the zone between the shore line and the fifteen fathom contour), 
ranged from about 32.6% to 35%p, lowest along the south shore of 
Fic. 36.— Chart of bottom salinity on the continental shelf between Cape 
Cod and Chesapeake Bay in July, and in the Gulf of Maine for August. 
Long Island, and off Block Island, highest, as might be expected, along 
the outer edge of the shelf. In a general way, it corresponded to 
depth; but there was also an unmistakable increase, independent of 
depth, from northeast to southwest. Thus a bottom salinity of 34%o 
was found at about the seventy fathom curve south of Nantucket, 
