AGASSIZ : THE FLORIDA ELEVATED REEF. 33 



Rodriguez and Tavernier Keys. At these points the elevated reef did not 

 rise more than about twelve inches above high-water mark, and presented 

 the same pitted and honeycombed appearance which characterized the 

 elevated reef elsewhere. The reef rock was full of pot-holes, and we 

 recognized as forming a part of the elevated reef blocks of the same 

 species of Orbicella, Mseandrina, Astrsea, and Colpophyllia characterizing 

 the elevated reef elsewhere. The elevated reef shelves very gradually to 

 the eastward, and at a distance of nearly half a mile from the shore we 

 could recognize it below water. 



In order to deteinnine, if possible, the width of the elevated reef, a 

 section was made across Key Largo extending from the low shore line 

 of the elevated reef to the east of Sound Point, at right angles to the 

 trend of the coast. Specimens were collected every 500 feet, and it was 

 found that the elevated reef extended about 3,000 feet from the shore. 

 Beyond that point the rocks collected seemed to indicate an asolian 

 formation blown into a shallow sink behind the elevated reef, much as 

 we observed it on some of the other keys, as at Key West, Boca Chica, 

 the Marquesas, and others, where the elevated reef has either been 

 eroded, or has been completely hidden by the sand thrown upon and 

 over its surface from the shore line and adjacent flats. 



This would seem to indicate a probable width of the Florida reef at 

 that point of at least nine miles from the outer reef patches, a width 

 of reef patches without parallel in any other coral reef district of the 

 "West Indies. 



The elevated reef crops out again near the eastern extremity of Elliott 

 Key (Plate VIII.). Its highest point is from five to six feet above 

 high-water mark. The part of the island where we landed is interesting, 

 as showing next to the elevated reef a small beach of coral sand over- 

 lappin the reef (Plate IV.). Judging from the aspect of the keys as 

 we steamed along, the reef alternately crops out or is covered by coral 

 sand, forming beaches in low places, or banks alternating with clusters of 

 mangroves and strips of land behind the elevated reef, separating the 

 inner sounds from the waters bathing the southern shores of the keys. 



The elevated reef is pitted, honeycombed, and full of pot-holes. From 

 what we have seen thus far the impression is produced that the outer 

 line of keys were once a part of one extended reef or patches of reef, 

 which formed a fringing or an edging reef off the southern edge of the 

 peninsula of Florida, and that the reef was subsequently elevated, and 

 the land thus raised eroded by the combined action of the rain and of 

 the sea. The process must have been very similar to that which gave 



