78 
FLORIDA STATE GEOLOGICAL SURVEY. 
One interesting feature of these corals, not already mentioned, is that they 
apparently bring the fauna of Vicksburg, Mississippi, into closer relation with 
the succeeding faunas. A great deal is shown regarding the succession and 
interrelations of the faunas of the continent itself. 
A bed in the lower part of the Chattahoochee formation usually 
contains an abundance of Bchinoids, and several different genera be¬ 
longing to this group are known to occur in other horizons. At a 
horizon about twenty feet above the echinoid bed there is a layer 
containing an abundance of gastropods belonging to the genus Helix, 
and a slightly higher horizon is characterized by numerous specimens 
of Cerithium. Among the fossils collected from this limestone are : 1 
Pyrazisinus cornutus. 
Cerithium hillsboroensis. 
Potamides trcmsecta. 
Conus planiceps. 
Natica amphora. 
Lucina hillsboroensis. 
Cardita serricosta. 
Venus st amine a. 
V. cancellata. 
V. penita, 
Cytherea nuciformis. 
Cyrena vesica. 
Orbitolites floridanus. 
Tagelus undet. 
Solen undet. 
Structure:—In northwestern Florida the limestones of the Chat¬ 
tahoochee formation dip toward the south. The exact amount of this 
dip is difficult to determine, but careful estimates by Miss Maury, 
based on sections made by Harris, places the average descent at 
twenty-three feet per mile. The same writer has noted a variation in 
the rate of dip, as will be seen from the following quotation: 
That this dip is steeper toward the north is shown by the following rate of 
slope: 
Aspalaga to ravine . 1.-8 mile, 10 feet, or 80 feet per mile. 
Aspalaga to Camp Scott. 2 miles, 70 feet, or 35 feet per mile. 
Camp Scott to Rock Bluff . 3 miles, 48 feet, or 16 feet per mile. 
Local Details:—The Chattahoochee formation, which is best ex¬ 
posed along the Apalachicola River, has been described by a number 
of writers. At Chattahoochee, according to Dali, the major portion 
of the rock exposed belongs to the Alum Bluff formation. His most 
complete section, which was made on the road running north from 
Chattahoochee Landing, is given below . 2 
1 Dali, Wm. H., and Stanley-Brown, Joseph; Cenozoic geology along the 
Apalachicola River; Bull. Geol. Society of Amer., vol. v, p. 153, 1894. 
2 Dali, Wm. H. and Stanley-Brown, Joseph. Cenozoic geology along the 
Apalachicola River, Bull. Geol. Soc. of Amer., vol. v, 1894, p. 152. 
