Freshwater Fish Zoogeography 
33 
1 Suwannee River 
2 Santa Fe River 
3 Orange Creek 
4 Little Orange Creek 
5 Levy's Prairie 
6 Oklawaha River 
7 Deep Creek 
8 Rice Creek 
9 Clark Creek 
10 Black Creek 
11 St. Johns River 
^ Northern Highlands 
il Trail Ridge 
@ Baywood Promontory 
H Duval Upland 
Fig. 3. Northeastern Florida, showing streams and topographic features asso- 
ciated with Cody Scarp and Trail Ridge. Although not specifically labelled here, 
Cody Scarp forms boundary of Northern Highlands, with Trail Ridge, Bay- 
wood Promontory and Duval Upland being situated beyond scarp limits. From 
Burgess and Franz (1978). 
timing and scale. There is no question that, in the past, peninsular Flor- 
ida was isolated by the sea from the rest of southeastern United States, 
and that the major break occurred in the northern part of the peninsula 
in the so-called “Suwannee Straits” area (Fig. 4). The principal evidence 
for former sea-level stands consists of geomorphic indications of actual 
shorelines (MacNeil 1949). There is also direct fossil evidence, since 
marine organisms are represented well inland from where the sea lies 
today (Alt and Brooks 1965, Robertson 1976). Furthermore, it is 
obvious that this isolation must have existed for a rather long time, as 
indicated by the level of genetic differentiation of many peninsular ele- 
ments from their close relatives to the north. Fishes furnish several good 
examples of this, as do other animal groups and various plants. 
