OCKLOCKNEE AND AUCILLA RIVERS. 
133 
numerous, and the progressive change from a subterranean to an 
open surface stream is seen in the occasional falling in of the. over- 
lying rock. The early stage in the stream development is illus¬ 
trated by the headwater tributaries of all of the drainage, basins. 
The smaller tributaries are surface streams which later become for 
a part of their course subterranean streams. 
THE ST. MARKS DRAINAGE SYSTEM. 
The. course of development of a drainage system under the con¬ 
ditions which are found in this area are well shown by the St. 
Marks River. This drainage system, with little doubt, formerly 
extended directly across Florida in a north-east south-west direc¬ 
tion. Its tributaries passing through the present Miccosukee and 
Lafayette basins. In this stage of its development this drainage sys¬ 
tem consisted wholly of surface flowing streams, no part, except 
possibly near the coast, touching the limestone, or flowing into it. 
Subsequently the channels of the streams were lowered to or nearly 
to the limestone and through the formation of sinks the streams 
were diverted into substerranean courses. In figure 11 is given* a 
sketch of the St. Marks drainage system as it may have existed at 
a comparatively early stage, before being diverted chiefly to a sub¬ 
terranean course. In figure 12 is given a sketch of this drainage 
system at the present time, when a large part of the drainage passing 
into Miccosukee, Lafayette and other smaller basins becomes sub¬ 
terranean. A late stage in the development of this system would 
show the streams again surface streams, although flowing at a lower 
level than the present land surface. 
Numerous other streams serve to illustrate stages in develop¬ 
ment from surface to subterranean streams and from subterranean 
again to surface streams. The. Aucilla River is chiefly an open 
channel stream lying at the limestone level, although some natural 
bridges yet remain. Wacissa River is likewise chiefly an open 
channel stream to its head at the Wacissa Springs. Pin Hook 
Creek in Jefferson County is an open stream for a short distance 
from the coast, beyond which its course at the present stage of 
development is marked by a succession of sinks and rises. 
