CHARACTERISTIC DEEP-SEA TYPES. — FISHES. 23 
Many surface fishes also descend to considerable depths. In 
fact, the migration of our coast fishes is one of the most impor- 
tant problems which the fisherman has to solve, and one of 
which we as yet know but little. There seems to be no seri- 
ous obstacle to extensive bathymetrie movements on the part of 
fishes. The silver hake, which is abundant all summer long at 
the surface on the New England coast, has been taken donne 
487 fathoms, and appears to live in September and October at 
considerable depths off Southern New England. "There is reason 
to believe that the mackerel, menhaden, “ed the bluefish also go 
down below the hundred-fathom line in winter. 
The fishes of the abyssal realm are very distinct from those 
of the surface faune. It is safe to say that there are more 
genera common to the seas of Australia and North America than 
to the littoral and abyssal fauna off the Atlantic coast of the 
United States, — excluding the pelagic types, many of which 
are cosmopolitan. Indeed, of the sixty or more genera which 
have been dredged below 1,000 fathoms in any sea, only one 
has been found in less than 200 fathoms on our own coast, and 
four within the two hundred-fathom line in any sea, even in 
polar regions. Of the same assemblage, only seven occur any- 
where in less than 300 fathoms, and down to 500 fourteen are 
added to the list. These fourteen genera represent ten fami- 
lies. Out of the thirty-four family groups which are répre- 
sented below 1,000 fathoms, or in mid-ocean beyond soundings, 
only five are represented in any in-shore fauna, even in circum- 
polar regions. 
We have now considered the composition of the abyssal 
fauna, as found at the greatest depths. A glance at its upper 
limits may also prove instructive ; we find below the hundred- 
fathom line, and within the limit of 500 fathoms, a very hete- 
rogeneous assemblage. Well-known surface species inhabit 
at times water of considerable depths. The cod goes below 
100 fathoms ; the halibut and the Newfoundland turbot go be- 
low 300, and the haddock apparently to 500, on the New Eng- 
land coast. Hake are also deep-sea lovers, being recorded at a 
depth of over 304 fathoms. One of the species of Phycis (P. 
regius) from 233 fathoms was discovered to be electric, giving 
