BIGELOW. — SHOAL- WATER DEPOSITS OF THE BERMUDA BANKS. 591 



sometimes plants, sometimes Foraminifera, and sometimes corals pre- 

 dominating"; and Mr. Finckh (p. 133), studying the biology of these 

 reef-forming ori^anisms, judges tlieir relative importance to be in the fol- 

 lowing order: (1) Lithothamnion, (2) Halimeda, (3) the Foraminifera, 

 (4) Corals. 



In dredging on the sea slopes of the Funafuti atoll Lithothamnion was 

 found abundant down to two hundred fathoms, and it plays a very im- 

 portant role in the modern reefs. One observation of particular interest 

 was on the growth of a cluster of Halimeda (p. 146), which in six weeks 

 attained a height and thickness of three inches. 



The most interesting feature of the report, as far as concerns our study 

 of the Challenger Bank, is the very great importance attaching to the 

 coralline algae, both in the modern reefs and in the older rocks, as shown 

 by the core from the borings. Putting aside all question as to changes 

 of level of the sea floor, there can be no doubt that the corallines, with 

 slight aid frona other organisms, are capable of building limestones of 

 great thickness ; and I believe that they will be found to enter into the 

 composition of most limestone banks, particularly those which, like Ber- 

 muda and the Challenger Bank, lie outside the belt of vigorous coral 

 growth. To complete the survey of what I may call the " Bermuda 

 range," it is most desirable that an examination should be made of the 

 Argus Bank, which rises to witliin eight fathoms of the surface. No 

 doubt, thanks to the shoal water, it will be found much more thickly 

 covered with corals and gorgonians than the Challenger Bank ; but in 

 all probability its foundations and structure are the same, and I think 

 we may consider the Challenger and Argus banks as two stages in the 

 growth of such an exposed peak as the Bermudas. 



Bibliography. 

 Agassiz, A. 



'88*. Three Cruises of the United States Coast and Geodetic Survey 

 Steamer "Blake," etc. Vol I. Bull. Mus. Comp. Zool. Harvard 

 Coll., vol. 14, xxii + 314 pp. 

 Agassiz, A. 



'88^ Three Cruises of the United States Coast and Geodetic Survey 

 Steamer " P>Iake," etc. Vo}. II. Bull. Mus. Comp. Zocil. Har- 

 vard Coll., vol. l.j, 1220 pp. 

 Agassiz, A. 



"94. A Reconnoissance of the Bahamas and of the Elevated Reefs of 

 Cuba, in the Steam Yacht " Wild Duck," January to April, 1803. 

 Bull. Mus. Comp. Zool. Harvard Coll., vol. 20, no. 1, pp. 1-203, 

 47 pis. 



