THE SHOAL-WATER DEPOSITS OF THE BERMUDA 



BANKS.* 



By Henry B. Bigelow. 



Presented by E. L. Mark, December 14, 1904. Received October 19, 1904. 



The sea-bottom deposits described in the following pages were col- 

 lected during the summers of 1903 and 1904 at the Bermuda Biological 

 Station for Research, to whose Director, Professor E. L. Mark, the writer 

 is indebted for many courtesies and much practical assistance. The col- 

 lection comprises seventy-six samples, the most of them preserved in 

 alcohol, dredged at sixty localities in the lagoons and sounds, and from 

 the beaches, of the Bermuda Pl.iteau, as well as the material taken in 

 twelve dredge hauls made during a three-days' expedition to the Chal- 

 lenger Bank. No attempt was made to secure samples in the deeper 

 waters on the sea faces of the banks. 



The general topographic features of the Bermudas have been thor- 

 oughly studied by Rein ('81), Heilprin ('89), and Agassis ('95), and I 

 shall commence with a brief resume of their accounts. The Bermuda 

 Bank (Map 1, p. 560) is oval in outline, its longest axis, which lies north- 

 east and southwest, being about thirty miles, and its breadth about fifteen ; 

 an area of some two hundred and seventy-five square miles. P'or the 

 purposes of the present description I shall consider the thirty-fathom line 

 as its limit, for at about that depth the abrupt slope to deeper oceanic 

 waters commences. The land mass, which consists of a number of 

 small islands, lies in a somewhat cresceotic form on the southern side 

 of the bank, where it forms an almost continuous barrier, but its entire 

 area is not more than fifteen thousand acres (less than 24 square miles). 

 Commencing at either extremity of the land mass and running thence 

 around the nortliern side of the bank, at about the twelve-fathom line, 

 some three miles inside the thirty-fathom line, is the so-called " boundary 

 reef," or " ledge flat." This is perhaps three-fourths of a mile in breadth, 

 awash in many places at low tide, and penetrated by several narrow 

 " cuts," of which the most important are " Hogfish," on the southwest ; 



* Contributions from the Bermuda Biological Station for Research, No. 5. 



