190 AGE OF COFAL REEFS. 



of successive concentric Reefs, we must believo 

 that hundreds of thousands of years have elapsed 

 since its formation began. Leaving aside, how- 

 ever, all that part of its history which is not 

 Fusceptible of positive demonstration in the pres- 

 ent state of our knowledge, I will limit my re- 

 sults to the evidence of facts already within our 

 possession ; and these give us as the lowest pos- 

 sible estimate a period of seventy thousand 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 them- 

 selves. What, now, do they tell us of the per- 

 manence 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, Maeandrinas, and Mad- 

 repores 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 Astraeans tfye differ- 

 ent Species of Astraea proper, forming the close 

 round heads, the Mussa, growing in smaller 

 stocks, where the mouths coalesce and run into 



