ffect upon distribution to height on the land.

The same idea is applied to the explanation of a similar anomaly in the
Fauna of the Aegean:--

"In the deepest of the regions of depth of the Aegean, the representation
of a Northern Fauna is maintained, partly by identical and partly by
representative forms.... The presence of the latter is essentially due to
the law (of representation of parallels of latitude by zones of depth),
whilst that of the former species depended on their transmission from
their parent seas during a former epoch, and subsequent isolation. That
epoch was doubtless the newer Pliocene or Glacial Era, when the _Mya
truncata_ and other northern forms now extinct in the Mediterranean, and
found fossil in the Sicilian tertiaries, ranged into that sea. The
changes which there destroyed the _shallow water_ glacial forms, did not
affect those living in the depths, and which still survive."[6]

[Footnote 6: _Memoirs of the Geological Survey of Great Britain_, Vol. i.
p. 390.]

The conception that the inhabitants of local depressions of the sea
bottom might be a remnant of the ancient population of the area, which
had held their own in these deep fastnesses against an invading Fauna, as
Britons and Gaels have held out in Wales and in Scotland against
encroaching Teutons, thus broached by Forbes, received a wider
application than Forbes had dreamed of when the sounding machine first
brought up specimens of the mud of the deep sea. As I have pointed out
elsewhere,[7] it at once became obvious that the calcareous sticky mud of
the Atlantic was made up, in the main, of shells of _Globigerina_ and
other _Foraminifera_, identical with those of which the true chalk is
composed, and the identity extended even to the presence of those
singular bodies, the Coccoliths and Coccospheres, the true nature of
which is not yet made out. Here then were organisms, as old as the
cretaceous epoch, still alive, and doing their work of rock-making at the
bottom of existing seas. What if _Globigerina_ and the Coccoliths should
not be the only survivors of a world passed away, which are hidden
beneath three miles of salt water? The letter which Dr. Wyville Thomson
wrote to Dr. Carpenter in May, 1868, out of which all these expeditions
have grown, shows that this query had become a practical problem in Dr.
Thomson's mind at that time; and the desirableness of solving the problem
is put in the foreground of his reasons for urging