yS FLORIDA GEOLOGICAL SURVEY-TWELFTH ANNUAL REPORT 
the bryozoa are much less liable to escape breakage. Many of the 
foraminifera are but a millimeter in diameter and enough of these 
remain intact so that most beds containing any number will give 
some identifiable specimens. The exception to this is the ease of 
hard limestones where often the specimens do not become loosened 
and the whole may be ground into a mass containing nothing of 
value for determinations. 
On the whole then the foraminifera are by far the best group 
for use in the study of well samples, from their small, size, thus 
more often appearing in recognizable form and their relative abun¬ 
dance in so many of the members of all the formations of the 
Coastal Plain from the Lower Cretaceous -to the Pleistocene. 
There are however barren stretches in all formations where 
not even foraminifera occur, especially the shore sands of various 
ages and chemically deposited limestones like the oolitic forma¬ 
tions. In addition to these the conditions of preservation may affect 
their usefulness. In certain beds greensands appear made up of 
the internal glauconitic casts of abundant foraminifera but not 
enough of the external characters remain for use in determination. 
Similarly in the older formations the changes made have left casts 
of silica or calcite which cannot be specifically determined. 
Also in the case of those beds which have abundant foramin¬ 
ifera, enough is not yet known in regard to the foramini feral 
faunas of various horizons to give a basis for close comparisons. 
This lack of information in regard to the Coastal Plain region is, 
however, being rapidly overcome and much unpublished data from 
my own work has been available for the present determinations. 
Another difficulty, especially in the case of southern Florida, 
is that the formations were deposited under different ecological 
conditions from those of northern Florida and adjacent states 
where the faunas are best known. As will be shown later, the 
formations of the Oligocene and older formations represented in 
the wells of the extreme southern part of Florida are not to be 
closely correlated with formations of our southern states but with 
tropical America, the West Indies and Central America. Detailed 
work in those areas is as yet hardly begun, but the comparisons 
as far as they can be made, indicate that close correlations are pos¬ 
sible. 
