357 The Oligocene of the Southern United States 47 



America, and named b\' him, Ntimmuliles Willcoxi*^ He found 

 later another species of the same ^enus, A^. Jfen'dcfisis, which is 

 less comnion than the former. The fragments of nnmmulitic rock 

 were bordered by a fringe of Pleistocene limestone with recent 

 freshwater shells indicating that the older deposit had been 

 Avorked over, but the latter was subsequently found in place 15 

 miles from the original locality, and has since been observed in 

 •several places and identified with the Ocala limestone. The 

 existence of Nunimulitic beds in the United States w^as thus 

 ■definitely established by Prof. Heilprin.f At Wheelers, on the 

 Homosassa River, a few miles from the Nummulitic beds, Prof. 

 Heilprin found a tough, horizontal limestone, full of Miliolidce, 

 The near association of the miliotitic and nummulitic beds leads 

 Prof. Heilprin to consider them almost equivalent. 



Beds analogous to the nummulitic deposits of central Florida 

 have been found silicified at Hawkinsville, Georgia, and on the 

 Suwanee river in Florida. | 



Chattahoochee Group. Langdori" s discovery of the Chattahoo- 

 chee beds. In 1887, Mr. D. W. Langdon discovered on the Chat- 

 tahoochee River, beneath the Orbitoides limestone, a formation 

 which he described as an "argillaceous and sandy limestone, 

 alternating with strata of purer chara<5ter. Contains a PcBen and 

 an Ostrea very close to our recent Virginica. This may be termed 

 the Chattahoochee group, as it is well developed there, and along 

 the eastern river bank for the next ten miles. "|j 



This deposit first appears nine miles above Chattahoochee 

 Jundlion and continues in sight to Rocky Bluff, where it dis- 

 appears. After Mr. Langdon's discovery of the Chattahoochee 

 group, beds belonging to this series, but previously confused with 



* Occurrence of Nummulitic deposits in Florida, Proc, A. N. 5"., July, 

 1882. (Species described earlier by Morton and Conrad as belonging to the 

 genus Numninlitea were really Orbitoides). 



t Explorations West Coast of Florida, Trans, //'c?^. Free hist. .Sri., 

 vol. 7, 18S7. 



j Dall, Loc. cit., p. 105. 



II Geoligical Se(Stion Chattahoochee River, in Gcol. Suri'ty Ga.y 1S90-91, 

 also Ai)ter. Jojtr. Sci., 3rd sen, 1889, vol. 38, p. 324. 



