5G6 PROCEEDINGS OF THE AMERICAN ACADEMY. 



with Foraminifera, Serpulae, and gasteropods, from 85 to 96 per cent of 

 the mass being calcic carbonate, and the remainder consisting of the 

 siliceous spicules of sponges, casts of Foraminifera and diatoms. Agassiz 

 ('95) has added to this description. He found some of the flats largely 

 formed of coraline, coral, and aeolian sand, and characterizes the deposits 

 westward of Wreck Hill and east of Ireland Island as a fine marl, similar 

 to that which he found in the Bahamas, off Andros Island (Agassiz, '94, 

 p. 253). Heilprin ('89) has called attention to the importance of mille- 

 pores as sand builders, and emphasized the importance of aeolian sand. 

 But beyond these no detailed study of the deposits has been made. 



For the purposes of the present paper the whole of the Bermuda Bank 

 falls naturally into four main topographic divisions: first, the land area, 

 of which only the beaches can be considered here ; second, the more or 

 less enclosed lagoons ; third, the shoals and flats inside the boundary 

 reefs ; and last, the area between these reefs and the thirty-fathom line. 

 Of this last area little examination was made, and our information is 

 only of a very general character. 



Commencing, then, with the beaches, a good example is afforded at 

 Newton's Bay, on the south shore, directly south of Harrington Sound. 

 This beach is of rather abrupt slope, the angle being about ten degrees, 

 and is composed of rather coarse shell sand, which has a pinkish color. 

 It consists chiefly of broken fragments of gasteropod and lamellibranch 

 shells, with many living gastero[)ods and a few bivalves ; the three most 

 important genera being Rissoina, Vermetus, and Tellina. Fragments of 

 large and small worm tubes are very numerous, and the pinkish color is 

 due to the great number of bits of a shining red Serpula. Incrusting 

 Bryozoa, nullipores, and corallines are important, and there are many 

 fragments of millepores, but few of any corals. Tests of large Foramin- 

 ifera occur, chitfly Orbitolites and Orbiculina, with a few smaller species. 

 In this sand there seems to be no fine material whatever ; probably it is 

 all washed away by the surf, which is often violent. At Tucker's Town 

 (Map 2), a fuw miles to the eastward, the surf is causing a rapid destruc- 

 tion of the cliffs, thereby adding to the sand a large amount of finely 

 ground material produced by the mechanical destruction of the aeolian 

 rock, which, being light and therefore easily wind blown, forms the bulk 

 of the modern dunes. The force of the winds here is well illustrated 

 by the large shells found blown many yards inland. Many of the 

 beaches contain enough serpuline fragments to give the sand a pink 

 color, as at Newton's Bay, and none are entirely free from such frag- 

 ments. A striking feature of all the beaches is the complete absence of 



