SECOND ANNUAL REPORT-—STRATIGRAPHIC GEOLOGY. 
59 
from a field where they were said to have been turned up by the plow. 
They represent a very cherty phase of the Marianna, and are probably 
the residual products of weathering. They consist of boulders up to 
two or three feet in diameter containing innumerable specimens of 
Orbit aides mantelli and Pecten poulsoni. 
At the phosphate mines in the vicinity of Croom, a number of 
specimens of Orhitoides mantelli were collected and the rock here 
has the lithologic characteristics of the “Peninsular” limestone. The 
collection was made from boulders dredged from a mine, and hence 
may not be sufficiently characteristic to decide whether this is “Pen¬ 
insular” or Ocala limestone. The presence also of a number of speci¬ 
mens of Cassidulus suggests that limestone belonging to the Apalachi¬ 
cola group is also represented. In the absence of characteristic num- 
mulites in the collections, it appears not unlikely that the limestones 
of the Apalachicola group may here rest upon the “Peninsular” lime¬ 
stone. However, this conclusion is made subject to revision in case 
future collections from this locality should reveal the presence of 
fossils belonging to the Ocala limestone. 
The “Peninsular” limestone is known to occur throughout the 
central part of the peninsula, where it may be observed in numerous 
natural and artificial exposures. It has been encountered in many of 
the hard rock phosphate mines from Croom northward nearly to the 
north line of the State. It is also known to underlie a large part of 
the central lake basin of the peninsula. This limestone is encountered 
in wells along the east coast from Fernandina southward beyond Palm 
Beach, and along the west coast south of Tampa. 
OCALA LIMESTONE (NUMMULITIC ROCK.) 
The Ocala limestone was formerly regarded as part of the “Or- 
bitoides” limestone, but in 1882 nummulites derived from waste prod¬ 
ucts of the Ocala limestone were described by Heilprin. The speci¬ 
mens were obtained by Willcox 1 on the Chassahowitzka River, and 
their association with fresh-water forms of recent shells was rightly 
interpreted to mean that the nummulites had been transported from 
some other locality and re-deposited with the younger shells. In 
1884, Willcox 2 announced the occurrence of the nummulitic rock in 
place some distance above the original locality on the Chassahowitzka 
River and Heilprin, in commenting upon the announcement, stated 
that the beds belonged to the Oligocene. 
1 Heilprin, Angelo. On the occurrence of nummulitic deposits in Florida, 
and the association of nummulites with a fresh water fauna. Acad, of Nat. Sci., 
Phila., Proc., 1882, pp. 189-193. 
2 Science, N. S., vol. iii, 1884, p. 607. 
