MUSEUM OF COMPARATIVE ZOOLOGY. 151 
tions, but basins of water of such profundity that they have not become 
closed by the swamp-building forces. The section of the lake district 
extends from near Waldo to Lake Kissimmee, or perhaps yet farther 
south. It has a length of at least two hundred miles and a width of 
about eighty miles, though its limits in each direction are obscure ; the 
area of open water basins gradually shades off into the area of the 
shallower depressions, now entirely occupied by swamps. By my rather 
untrustworthy barometric observations, the highest point of the surface 
in this lake district in the region about Apopka rises to near three hun- 
dred feet above the sea. The number of basins contained in the area is 
very great. If all those containing permanent open water were enumer- 
ated, the total would probably amount to several thousand. In size 
they vary, from the larger bodies, such as Lake Apopka, with a diameter 
of ten miles or more, down to basins a few score feet across. 
The most interesting feature in this district is the increase in the 
measure of irregularity in the hills, as we rise above the sea level. On 
either side, in passing from the shore, we cross a region which, though 
occupied by sands, has, as before noted, a gently rolling aspect, remind- 
ing one of the undulations of the sea when the waves of a great storm 
have nearly sunk to rest. This is the condition of surface for a height 
of from ten to thirty feet above the shore. For each fifty feet of as- 
cent, careful observation shows a decided increase in the amount of the 
irregularities, until they attain their maximum relief in the uppermost 
portion of the country. So far as I have been able to ascertain, sub- 
stantially all of these irregularities are moulded in recent sands. Only 
occasionally are they affected by the form of the surface which existed 
before the drifting sands came to this region. In certain cases the 
underlying rocks are of a calcareous nature, and have been eroded by 
subterranean waters. Where this has occurred, the pits formed in the 
sands have occasional s¢xk-holes in their bottoms. Some scores of such 
openings were seen in the course of four days’ journeying between 
Seville and Lakeland, in Polk County. It seems to me, however, that 
these pits are not in any measure due to the causes which produced the 
sink-holes. The great variety in their size, the lack of order in their 
disposition on the surface, as well as the chance sections afforded by 
railways, all indicate that the sink-holes are occasional concomitants of 
these depressions, and in no sense their cause. My observations show, 
moreover, that the sink-hole openings are often in eccentric positions in 
relation to the pits, in some cases being actually above the lowest point 
of the depression. 
