Ill 



been united to the mainland by the complete fiUing up and consolidation of 

 the channel which once divided it from the extremity of the peninsula, as a 

 channel now separates the Keys from the Shore-bluffs, and the outer reef 

 again from the Keys. These three concentric reefs, then, — the outer reef, 

 the Keys, and the Shore-bluffs, — if we measure the growth of the two latter 

 on the same low estimate by which I have calculated the rate of progress of 

 the former, cannot have reached their present condition in less than twenty 

 thousand years. 



"But this is not the end of the story. Travelling inland from the 

 Shore-bluffs, we cross a low, flat expanse of land, the Indian hunting- 

 ground, which brings us to a row of elevations called the Hummocks. This 

 hunting-ground, or Ever-glade, as it is also called, is an old channel 

 changed first to mud-flats and then to dry land, by the same kind of 

 accumulation that is filling up the present channels, and the row of 

 Htimmocks is but an old Coral reef with the Keys, or islands, of past days 

 upon its summit. Seven such reefs and channels of former times have 

 already -been traced between the Shore-bluffs and Lake Okee-cho-bee, 

 adding some fifty thousand years to our previous estimate. Indeed, upon 

 the lowest calculation, based upon the facts thus far ascertained as to their 

 growth, we cannot suppose that less than seventy thousand years have 

 elapsed since the Coral reefs already known to exist in Florida began to 

 grow. So much for the duration of the reefs themselves. What, now, do 

 they tell us of the permanence of the species by which they were formed? 

 In these seventy thousand years has there been any change in the Corals 

 living in the Gulf of Mexico ? I answer most emphatically, No. Astraeans, 

 Porites, Mseandrinas, and Madrepores, were represented by exactly the 

 same species seventy thousand years ago as they are now. "Were we to 

 classify the Florida Corals from the reefs of the interior, the result would 

 correspond exactly to a classification founded upon the living Corals of the 

 outer reef to-day. There would be among the Astrseans the different species 

 of Astrsea proper, forming the close roundheads, — the Mtcssa, growing in 

 smaller stocks, where the mouths coalesce and run into each other, as in 

 the Brain-Corals, but in which the depressions formed by the mouths are 

 deeper, — and the Caryophyllians, in which the single individuals stand out 

 more distinctly from the stock; among Porites, the P. Astrceoides, with 

 pits resembling those of the Astrseans in form, though smaller in size, 

 and growing also in solid heads, though these masses are covered with 

 club-shaped protmsions, instead of presenting a smooth, even surface, like 

 the Astrseans, — and the P. Clavaria, in which the stocks are divided in short 

 stumpy branches, with club-shaped ends, instead of growing in close 

 compact heads; among the Mseandrinas we should have the round -heads 

 we know as Brain-Corals, with their wavy lines over the surface; and 

 the Manicina, differing again from the preceding by certain details of 



