30 FLORIDA GEOLOGICAL SURVEY TENTH ANNUAL REPORT. 
and is exposed on the Apalachicola and Ocklocknee rivers. It dips 
and passes below the surface before reaching the Gulf. The Apa- 
lachicola river, which forms the western boundary of this area, 
flows across this limestone from the State line to somewhat below 
Rock Bluff in Liberty county, where the limestone passes below 
water level. The Ocklocknee river at the east side of the area 
flows on this formation from the State line to the crossing of the 
Seaboard Air Line Railway, where the rock passes below water 
level. Although exposed on these river channels, in the hills and 
on tributaries for some distance back from the main streams, the 
formation elsewhere in this area is concealed by the later forma- 
tions. 
The fossils of the Chattahoochee formation are, for the most 
part imperfect. Of vertebrates, no recognizable species have been 
obtained, although broken pieces of ribs, probably of cetaceans, are 
not uncommon. Invertebrates are not numerous in the formation 
as exposed in this area, and are preserved, for the most part, as 
casts. 
SURFACE EXPOSURES OF THE CHATTAHOOCHEE LIMESTONE. 
As already noted, the principal surface exposures of the Chat- 
tahoochee limestone are those found on the channels of the Apa- 
lachicola and Ocklocknee rivers. The exposures on the Apalachi- 
cola river were described in some detail in the Second Annual 
Report of the Florida Survey.* Some of the more important of 
the sections on the Apalachicola river, so far as they include this 
formation, are here reproduced from this earlier report. Among 
the localities where exposures of this formation may be seen are 
Chattahoochee Landing, Aspalaga Bluff and Rock Bluff. In all 
of these sections the measurements were referred to the. water level 
at the stage of March 5, 1909. At that time the water on the gauge 
at the railroad bridge at River Junction was 7/4 feet, or about 51 
feet above sea level. 
* The Fullers Earth Deposits of Gadsden County, with notes on similar 
deposits found elsewhere in the State. By E. H. Sellards and Herman Gun- 
ter, Fla. Geol. Surv., 2nd Ann. Rpt., pp. 253-291, 1909. 
