578 PROCEEDINGS OF THE AMERICAN ACADEMY. 



any kind on tliis bottom, and their remains have added but slightly to it. 

 The fine silt consists of the detritus from the destructive action of the 

 water on the surrounding limestone reefs and ledges. In the southern 

 and southeastern part of the lagoon, through which the Ship Channel 

 runs, the character of the bottom is very different. We find here also, 

 at Station 1416, in seven fathoms, a wliite sand, but it is much coarser, 

 containing large quantities of corallines, molluscan shell fragments, and 

 many living bivalves and gasteropods, witli bits of worm tubes, plates 

 of echinoids, millepore fragments, and a few large Foraminifera, chiefly 

 Orhiculina and Orbitolites. There is about 10 per cent of fine calcareous 

 silt, containing some spicules of sponges and gorgonians, which is similar 

 in nature to the white marl of the northern half of the lagoon. This 

 shell sand extends westward along the Ship Channel, at a depth of about 

 eight fathoms, into the so-called " Brackish Pond Flats," directly north 

 of the Flatts Inlet. In this inlet itself (Statiou 393), the very strong 

 tidal fiow has effectually scoured out all the finer materials, leaving only 

 the coarser fragments. From the Ship Channel southward toward Crawl 

 Point and Bailey's Bay, the water gradually shoals to about four fathoms ; 

 about a mile off shore, in seven fathoms (Station 00 ?), we again find 

 the white marl bottom already described for the region north of Murray 

 Anchorage. There are here more large shell fragments and more living 

 Orbitolites and Orbiculina than in the more northern area, but organisms 

 in general are very few. The proportion of calcareous sponge and gor- 

 gouian spicules is considerable ; the rest of the deposit, about 60 per 

 cent, consists of very fine water-worn silt. 



Still nearer the shore, around the ledges known as the " Pigeon 

 Rocks," about half a mile from Crawl Point, at Stations 411, 412, and 

 416, in about three fathoms, shell sand again occurs, the bottom being 

 very clean, with less than 5 per cent ooze, though varying much in coarse- 

 ness, some of it being very fine indeed. The transition from marl, at 

 Station 00 ?, to this deposit of sand is very sudden, and is no doubt due 

 to the shoaling water and the surf action around these detached ledges. 

 About one mile to the eastward, at the mouth of Bailey's Bay (Station 

 317) in two to three fathoms the bottom is again coherent, having 30 

 to 40 per cent ooze and being light gray. The coarse material con- 

 sists chiefly of moUuscan fragments and Foraminifera, with a few living 

 bivalves, gasteropods, and fragments of echinoids and corallines. This 

 station and the Bay itself are sheltered localities, where fine silt is 

 readily deposited. 



Close in alonjT the shores of the main or Bermuda Island and St. 



