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BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



separated by a scarp from the 28 to 36 fathom flat, and by another scarp from the 

 shallower levels in Tortugas. The presence of the continuous scarp from Coalbin Rock 

 to off the west end of the Quicksands, with a depth of 25 to 30 fathoms at its foot, and 

 the presence of a terrace 28 to 36 fathoms deep, 10 miles wide, and bounded on its land- 



Fig. 18.— Chart of northern end of floridian barrier reef. From United States coast and 

 geodetic survey chart no. 165. 



ward margin by a similar scarp, suggest that the portion of the Florida reef tract west 

 of Key West at one time stood some 20 fathoms higher than now, while the 15 to 18 

 fathom terraces suggest another, shallower stand of sea level. 



Although the tracing of the oscillations of the Florida reef tract can not now be 

 made in detail, it seems probable that it at one time stood more than 120 feet higher 



