278 



BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



The reefs of the St. Martin Plateau are superposed on an ante- 

 cedent platform that was brought into its present relations to sea 

 level by geologically Recent submergence to an amount of about 20 

 fathoms. 



Fig. 13.— Chart of virgin islands and st. croix. From U. S. hydrogramiic chart no. 2318. Scale, 



ONE INCH^AEOUT 12.8 NAUTICAL MILES. 



ST. CROIX ISLAND. 



This island rises above a bank about 30 miles long and 10 miles 

 wide. The distance from the shore to the 100-f athom curve is usually 



