10 BULLETIN 90, UNITED STATES NATIONAL MUSEUM. 



the surface of the lowland limestone at the foot of the ridge; and 

 that water was struck only at a further depth corresponding to the 

 Avater level in the lowlands. This may indicate that the ridge corre- 

 sponds rather to dune formation, or residual material left after 

 solution in adjacent low areas, than to any real orogenic fold. While 

 minor folding of a gentle character was observed by me along the 

 banks of the Caloosahatchie Eiver between Lake Okeechobee and the 

 Gulf of Mexico, nothing indicating a major fold corresponding to 

 the western ridge (which reaches in places a height of nearly or 

 quite 200 feet) was detected. 



The limestone characterized by a great abundance of Orhitoklen 

 (Lepidocyclina) which is the fundamental rock of peninsular 

 Florida, and which has (p. 6) been shown to be, faunally, meas- 

 urably distinct from the two horizons at Vicksburg included by 

 Conrad in his Vicksburg Group, as indicated previously was named 

 by me the Peninsular limestone. Messrs. Matson and Clapp con- 

 sidered it desirable to unite certain limestones of western Florida, 

 which they called "Marianna limestone,^' with the Peninsular lime- 

 stone which they believed might be newer than the Marianna, with 

 the continuously deposited Nmnmulitic or Ocala limestone which is 

 believed to be at least the latest faunal phase of the Peninuslar 

 limestone; and presumably also with the two typical Vicksburg 

 horizons of Conrad — in one group, which "to avoid further con- 

 fusion " they proposed to call the Vicksburg Group. 



There is no doubt of the relationship faunally of these several 

 strata, but if we combine them into one group without indicating by 

 any subordinate names the individual characteristics of the several 

 zones referred to, it would seem that clearness would rather be lost 

 than gained. 



The different points of view outlined above account for the differ- 

 ent results arrived at by the respective authors. 



The column as devised by Messrs. Matson and Clapp is as follows : 



MIOCENE. 



Jacksonville formation. Clioctawhatchee marl. 



= Unconformity. 



OLIGOCENE. 



Apalachicola Group. 



Alum Bluff formation. 



I Chattahoochee formation. 

 Hawthorne formation. 

 Tampa formation. 

 — Unconformitj'. 



i Ocala limestone. 

 Peninsular limestone. 

 Marianna limestone. 



