ORIGIN OR THE HARD ROCK PHOSPHATES. 
39 
tions in Florida. In the present discussion the writer is particu¬ 
larly indebted to Dali's observations, recorded in Bulletin 84 of 
the United States Geological Survey, pages 109, 110 and 111, of 
remnants of the Upper Oligoeene formations (then classed as 
old Miocene) at Levyville, in Levy County, at Fort White, in 
Columbia County, and near Archer, in Alachua County. These 
localities lie west, north and east of the northward extension of 
the phosphate fields, and Dali, in the map which accompanies this 
report, represents the old Miocene as extending directly across 
the northern end of the hard rock phosphate area, with local 
exposures of the Vicksburg formation. These observations by 
Dali are accepted by the writer and form a part of his argument 
that the Upper Oligoeene (old Miocene) formerly extended 
across the phosphate fields as a whole. 
Messrs. George C. Matson and F. G. Clapp, in connection with 
cooperative work carried on by the United States Geological 
Survey and the Florida State Geological Survey, have added im¬ 
portant observations regarding the former areal extent of the 
Upper Oligoeene formations in Central Florida, remnants of these 
formations having been noted by them at many of the phosphate 
mines of Central Florida. Dr. T. W. Vaughan, of the United 
States Geological Survey, under whose supervision these co-opera¬ 
tive investigations were carried on, has given material assistance 
in determining the stratigraphic succession in Florida both by 
directing the field work and by the identification of fossils and 
of formations. 
Of the many other publications on the phosphates of Florida 
all of those of which a record has been obtained are listed in the 
bibliography, which follows this paper. In addition, those rela¬ 
ting directly to the origin of the hard rock phosphates are reviewed 
in connection with a discussion of the theories previously 
advanced; reference to a number of the papers on the Florida 
phosphates is included in the notes in regard to the discovery, 
investigation and development of the phosphate deposits. In out¬ 
lining, on the accompanying map, the probable extent of the land 
pebble phosphates of Southern Florida the writer has utilized, 
