GEOGRAPHY OF CENTRAL FLORIDA 1 63 



rocky type in the hammock behs. Those with permanent water in 

 them are apparently more common in northern than in central Flor- 

 ida, bnt examples can be seen near Sumtei"ville and Lacoochee. 

 In the Hernando hammock belt some of the intermittent lakes or 

 prairies have a small rocky lime-sink at one end or edge, through 

 which the water drains off (fig. i6). There are said to be some 

 lime-sinks on the west side of Lake George, which the writer has 

 mapped as being in the lake region, but not yet explored. 



Caves. Limestone caves are not uncommon in and near the 

 hammock belt in jMarion County, and there are a few small ones 

 in the southeastern part of Citrus County,* hardly large enough 

 to contain stalactites and stalagmites or to be easily entered. 



Natural bridges in central Florida are of two types, which might 

 be called wet and dry. The former is the commonest, and is caused 

 by a stream entering a subterranean channel made by solution of 

 limestone, which it may follow anywhere from a few rods to a few 

 miles. It is of course impossible to go under such a bridge, and 

 sometimes one cannot even be sure where a disappearing stream 

 emerges again. Bridges of this type are reported near Homosassa 

 and Tarpon Springs, and there must be many unrecognized ones 

 made by small streams. A rarer and very different type is formed 

 by blocks of limestone falling against each other when the ground 

 under them settles irregularly from the slow solution of still deeper 

 calcareous strata. A few of this kind can be seen in the neighbor- 

 hood of the caves of southeastern Citrus County just mentioned. 



Flatzcoods. Most of the country within twenty miles or so of 

 the coast on both sides of the peninsula is essentially level, except 

 where shallowly dissected by streams. The dissection is most pro- 

 nounced near the^ Peace and Alafia Rivers, and at certain points 

 near the coast where the general level of the country is 20 or 25 

 feet above the sea. as at Eau Gallic, Melbourne, and St. Petersburg. 

 The flatness is probably due to the fact that the sand and underlying 

 materials were deposited on a nearly level ocean bottom, and have 

 not been elevated high enough or long enough to be eroded much. 



Beaches and dunes. The whole Atlantic coast of central Flor- 

 ida and the Gulf coast in Pinellas County, are bordered by rather 



*For additional information about these see R. JNI. Harper, Am. Fern 

 Journal 6:68-81. 1916; Natural History (formerly American Museum Jorr.ial) 

 2:201. 1919; J. K. Small, Jour. N. Y. Bot. Gard. 21:34-37. iQ-^o. 



