56 
FLORIDA STATE GEOLOGICAL SURVEY. 
been explained in a previous paper,* the limestone country of 
Central Florida is gradually encroaching on the non-limestone 
country. These temporary streams make up one of the character¬ 
istic features of the physiography in the transition stage and num¬ 
erous examples of such streams are found in the partially eroded 
uplands bordering the phosphate fields. After being formed a 
sink is frequently filled up by the materials carried by the stream 
which enters it. 
In addition to local streams it is probable that considerable 
bodies of water existed from time to time in this section into which 
streams entered. The Pliocene was probably the time of the most 
active reaccumulation of the material which makes up the matrix 
of the phosphate deposits. Whether or not this area was partially 
submerged during the time of the reworking of the materials of 
this formation can possibly be determined by a careful study of 
the fossils. 
THE FOSSILS OF THE HARD ROCK PHOSPHATE 
DEPOSITS. 
Two distinct groups or lots of fossils are found in this forma¬ 
tion. The first of these includes those fossils, chiefly sharks’ teeth, 
that are residual from the formations that have disintegrated. The 
second group, of which there is a considerable fauna, chiefly land 
animals, includes those fossils that were incorporated in connec¬ 
tion with the reworking of the materials. The invertebrate fossils 
of this formation are contained for the most part in loose frag¬ 
ments of rock which represent inclusions from the underlying 
Vicksburg Limestone or remnants from later formations that 
have disintegrated. 
It should be borne in mind in this connection that the residual 
fossils do not necessarily all come from formations later than the 
Vicksburg. A part, possibly a majority, are residual from the 
Vicksburg itself. As already explained, the limestone is being 
constantly removed by solution and the fossils that it contained, 
if sufficiently resistant, remain as a part of the residue and hence 
^'Fourth Annual Report Florida Geological Survey, page 33, 1912. 
