40 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
This would allow the gradual formation of more or less deep channels, 
slowly increasing in width and in depth, through which material held in 
suspension or solution could pass out and be deposited on the sea face 
of the sounds, the sea encroaching upon the shores of the sinks forming 
more and more distinct sounds, or even huge open bays like Key Biscayne 
Day, separated from the sea by a barrier of sand bores completely cover- 
ing the eroded part of the elevated reef which once flanked the bay 
from Key Biscayne westward, and of which Soldier Key, the Ragged 
Keys, and Elliott Key are the remnants (Plate XIII.). 
Some of the larger and inore extensive sinks characteristic of the 
southern part of Florida may be due to folding occurring at the time 
of the elevation of the reef forming the backbone of the larger Florida 
Keys. Yet some of the sinks and sounds undoubtedly owe their origin, 
not to the folding, as suggested by Mr. Griswold, but to the decomposi- 
tion by water of the æolian rock deposited in the sinks, and to the 
subsequent disintegration due to the carrying off of limestone, either in 
solution or in suspension, through channels leading into open water. 
Key Discayne, Virginia Key, Soldier Key, and the Ragged Keys remain 
to attest the former existence of an extensive series of broad low keys, 
the position of which is indicated by the wide and shallow bank that 
separates Key Biscayne Bay from the waters of the Gulf Stream north 
of Sands and Elliott Keys (Plate XIII). The numerous deep channels 
separating the banks to the westward of Key Biscayno undoubtedly 
indicate the position of cuts similar to Bear Cut, which divides Virginia 
Key from Key Biscayne. These keys have been eroded and the material 
which forms the sand bores that cover the sunken surface of the ele- 
vated reef has been brought by the currents from the low land which 
once occupied the interior of the sounds. The meeting of the sea, due 
to the prevailing winds, with the currents flowing out of Key Biscayne 
Зау has resulted in the deposition of the material they carry, the 
one on the sea face of that key, the other on the banks to the 
southward. 
The spurs which extend in a northerly direction from the west side of 
Key Largo (Plate XII.), some of which extend to the mainland, plainly 
indicate the manner in which the line of keys has gradually become dis- 
connected from the peninsula of Florida. The western part of Card’s 
Sound is still separated from the sink of Barnes Sound by a continuous 
strip of land, and further by a series of smaller secondary sounds which 
will in time disappear with the erosion of the more or less disconnected 
dividing land strips. This will leave on that part of the flats only such 
