32 
Carter R. Gilbert 
one may assume that (a) it limited the southern distributions of many 
species, and (b) the four species listed above by-passed the Satilla and 
St. Marys via the upper Suwannee River, from where they subsequently 
entered the lower (i.e., northern) St. Johns drainage by way of the Santa 
Fe River system (Burgess and Franz 1978). Although some lotic spe- 
cies, such as Noturus leptacanthus and Minytrema melanops, later 
gained access to the St. Marys and/or Satilla, this does not negate the 
present hypothesis. 
The break between the Apalachicola River and those drainages 
immediately to the east (Altamaha, Suwannee and Ochlockonee) is the 
most significant faunal break in the area of study, showing a coefficient 
level of only 0.29. This is particularly surprising in the case of the Apa- 
lachicola and Ochlockonee, inasmuch as the Coastal Plain habitat, with 
its poorly defined drainage divides, appears to offer easy passage in 
both directions to a large number of lowland species. Furthermore, the 
Ochlockonee River, in Florida, appears to have captured its western- 
most tributary, Telogia Creek, from the Apalachicola River. Evidence 
for this may be seen from the geographic appearance of Telogia Creek, 
the upper section of which flows in a southwesterly direction toward the 
Apalachicola, then doubles completely back on itself to take a northeast- 
erly course to the Ochlockonee (Swift et al. 1977: Fig. 1-2). Several 
species of western affinities that typically occupy flowing streams of 
varying size (e.g., Ichthyomyzon gagei, Notropis t exanus, Notropis 
venustus, Semotilus thoreauianus and Etheostoma swaini ) presumably 
entered the Ochlockonee drainage via this route (Rohde and Lanteigne- 
Courchene 1980, Swift 1980b, Gilbert and Burgess 1980b, Lee and Pla- 
tania 1980, Starnes 1980). Overall, however, the fish faunas of the Apa- 
lachicola and Ochlockonee are quite different, a situation that suggests 
long-term physiographic independence of these drainages. Price and 
Whetstone (1977) indicate that the Apalachicola River (which upstream 
is called the Chattahoochee River) has maintained its basic integrity 
throughout the latter half of the Cenozoic, and has remained deeply 
entrenched in its southerly course since it was rapidly eroding down- 
ward in a positive area of terrestrial rise. The long-term phys- 
iographic integrity of the Apalachicola would thus tend to preserve its 
biological integrity as well. 
GEOGRAPHICAL ISOLATION AND ENDEMISM 
IN PENINSULAR FLORIDA 
Past discussion of the zoogeography of the south Georgia-peninsular 
Florida area has been complicated by the fact that interpretations of 
major sea-level cycles have frequently been modified with regard to both 
