GHOGRAPHICAL DISTRIBUTION. 665 
Acadian fauna and a few in the Virginian fauna, as the 
Labrador or polar current passes down along the coast, 
bathing the New England coast north of Cape Cod, and 
even extending under the warm surface-water as far as New 
Jersey. On the other hand, the great volume of heated 
tropical water forming the Gulf Stream issuing from the 
Straits of Florida makes its influence most sensibly felt as 
far as Cape Hatteras, and in a diminished degree to Cape 
Cod, and even southern shells, etc., are found as outliers of 
more southern faune near Portland, Me., and Nova Scotia. 
As we descend from the shore into deep water, the tem- 
perature becomes lower and lower the deeper we go, until 
we come toa stratum or zone of water about 32°-36° Fahr., 
where circumpolar or arctic life alone abounds. Wherever 
deep abysses off the coast or at the bottom of bays or gulfs 
occur, the water is found to be colder than elsewhere ; just 
as when we ascend a mountain the air becomes colder, un- 
til at the Alpine summits we find an arctic temperature 
and fauna; thus, in the sea, increase of depth is paralleled 
by increase of height on land. 
Usually, off the coast of the United States, north of New 
York, there is a distinct zone of life between high and low 
water, a second extending to the depth of about fifty fathoms, 
anda third to one hundred fathoms or over. Ata depth of 
from one or two hundred fathoms in the Northern Atlantic, 
and from five hundred to one thousand fathoms in the sub- 
tropical and tropical seas, down to the deepest parts of the' 
ocean, now known in a few points to be about five miles in 
depth, the water is about 32° Fahr. and the animal life is 
polar in its nature. The water of the ocean all over the 
globe, as shown by the results of the ‘‘ Challenger’? and 
other expeditions for the exploration of the sea at great 
depths, everywhere below a depth of one thousand fathoms, 
is of an arctic temperature, overlaid by the heated water of 
the tropics. The abysses or deeper parts of the ocean-bed 
support a nearly uniform assemblage of life, which may be 
called the deep-sea or abyssal fauna. The animals largely 
consist of Echinoderms, notably Crinoids, with Coslenterates, 
mollusks, worms, and Crustacea, and it is an interesting fact 
