BIGELOW. — SHOAL-WATER DEPOSITS OF THE BERMUDA BANKS. 575 



Little Sound, situated directly south of Great Sound and forming a 

 basin about two miles long, with a greatest depth of ten or eleven fathoms, 

 is in many respects similar to INIullet Bay. On the south, east, and west 

 it is bounded by the shores of Long or Bermuda Island ; its eastern edge 

 is formed by a broad and very shallow flat, with three small islands ; and 

 on the north it is separated from Great Sound by a shoal and narrow bar, 

 over which the greatest depth of water is three fathoms. There is no 

 channel cutting this bar, so that the sound is a practically enclosed basin. 

 The bottom at Station 366, in nine fathoms, is composed of a fine, sticky 

 blue mud, made up of extremely minute particles, most of which are 

 of terrigenous origin. But I was able to distinguish also the tests of a 

 few small Foraminifera, as well as a large number of calcareous sponge 

 and gorgonian spicules, and fragments of Halimeda. The only large frag- 

 ments were a few broken and water-worn lamellibranch shells, and the 

 bottom contains very few living organisms. It is evident from the nature 

 of the bottom that its origin is very similar to that of Mullet Bay, and 

 that much of the mass consists of terrigenous detritus washed down from 

 the hills which form its southern shore. The topography of Little Sound 

 is such that it has acted as a catch-basin for this material and also for the 

 fine calcareous silt from the outer lagoons and reefs, carried in suspen- 

 sion by the sea water. The absence of living organisms is the result of 

 a choking process caused by the rapid deposition of silt all over the 

 bottom ; and in such a locality the remains of resident animals are of 

 very slight importance in forming the bottom deposits. 



Hamilton Harbor shows somewhat similar conditions, with a bottom 

 of the same type. There is also another basin of this type which, though 

 very much smaller, has a depth of nine fathoms ; it is known as '' Grana- 

 way Deep," and lies directly south of Marshall Island. 



Harrington Sound is more completely landlocked than any of the 

 basins hitherto described. At its southwest corner it connects with the 

 open lagoon through the " Flatts Inlet," a channel barely sixty feet wide, 

 and by several smaller subterranean passages. I cannot make any esti- 

 mate of the amount of water which passes in and out through these 

 channels, but in certain parts of the sound the tidal currents are of ap- 

 preciable strength. Strangely enough, in spite of its landlocked con- 

 dition, this sound is one of the richest localities for invertebrate life ; 

 from which we must draw the conclusion that its circulation of sea water 

 is probably much greater than the narrowness of the known passages 

 connecting it with the outer lagoon would indicate. The greatest depth 

 is said by Heilprin ('89) to be sixteen fathoms ; most of the basin is 



