58 FLORIDA EEEFS. 



began. Leaving aside, however, all that part of its history which is not sus- 

 ceptible of positive demonstration in the present state of our knowledo-e, I 

 will limit my results to the evidence of flicts already within our possession ; 

 and these give us as the lowest possible estimate a period of seventy thou- 

 sand years for the formation of that part of the peninsula which extends 

 south of Lake Okee-cho-bee to the present outer reef. 



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 livino- 

 in the Gulf of Mexico ? I answer most emphatically, No. Astrjeans, Porites, 

 Maeandrinas, 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 Astra)ans the different species of 

 Astrtea (PI. IV.) proper, forming the close, round heads, — the Mussa, grow- 

 ing 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 (Cladocora PI. III., Figs. 1-7), in which 

 the single individuals stand out more distinctly from the stock ; among 

 Porites, the P. Astracoides (PI. XVI., Figs. 1-12), with pits resembling those 

 of the Astraeans in form, though smaller in size, and growing also in solid 

 heads, though these masses are covered with club-shaped protrusions, instead 

 of presenting a smooth, even surface like the Astrtcans, — and the P. Cla- 

 varia (PI. XII., Figs. 4, 5, and 6), in which the stocks are divided in short, 

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

 pact heads; among the Mreandrinas we should have the round heads we 

 know as Brain-Corals (PI. IX.), with their wavy lines over the surface, and 

 the Manicina (Pis. V., VI.), differing again from the preceding by certain 

 details of structure ; among the Madrepores we should have the Madrepora 

 prolifera (PI. XIX.), with its small, short branches, broken up by very fre- 

 quent ramifications, the M. cervicornis (PI. XVIII.), with longer and stouter 

 branches and less frequent ramifications, and the cup-like M. palmata (PI. 

 XVII.), resembling an open sponge in form. Every species, in short, that 

 lives upon the present reef is 'found in the more ancient ones. They all 

 belong to our own geological period, and we cannot, upon the evidence 

 before us, estimate its duration at less than seventy thousand years, during 



