572 PROCEEDINGS OP THE AMERICAN ACADEMY. 



increasing rapidly toward the mouth ; a sample from the middle of the 

 opening (Station 1409, four fathoms), just at the mouth, has only a very 

 faint bluish tinge. It is rather coarse, clean, granular, with 1 per cent 

 fine silt. Foraminifera make up 10 per cent, and millepores and algae, 

 in nearly equal proportion, about 40 per cent; the remainder consists of 

 bivalve and gasteropod fragments, Serpula, Polyzoa, echinoid fragments 

 and small water-worn fragments of limestone from the cliffs. There are 

 many living organisms in this bottom, especially Foraminifera and 

 gasteropods, but the greater portion of the deposit consists of the 

 coarser reef detritus from the neighboring ledges. 



Mullet Bay, on the northwest side of St. George's Harbor, is a small 

 nearly enclosed body of water cut off by a very shoal bar and with no 

 tidal currents. Tiie depth over the bar is about seven feet, that inside 

 the bay nearly three fathoms. The bottom (Station 355) consists of a 

 sticky and very fine blue mud, which is chiefly if not entirely calcareous. 

 The fragments of which it is composed are so minute as to be wholly 

 indistinguishable to the naked eye. Large numbers of Toxopneustes 

 live in this mud, and it contains great quantities of their plates and 

 spines, but there are few if any other conspicuous living organisms. 

 The character of the mud shows conclusively that it is chiefly terrigenous 

 silt and detritus washed down from the surrounding hills, and it corre- 

 sponds perfectly in its occurrence and origin to the siliceous " blue mud" 

 of the continental slope, its calcareous nature being of course explained 

 by the fact that the land mass consists entirely of limestone rocks. 



Dolly's Bay (Station 1408), another partially landlocked bight of a 

 similar character, has a bottom of the same type consisting almost 

 entirely of sticky blue mud, with a few echinoid plates and spines. In 

 Smith's Sound (Station 1407), which connects Dolly's Bay with St. 

 George's Channel, the bottom is of similar constitution, but much 

 coarser, with a considerable number of both broken and living shells and 

 an appreciable proportion of the spicules of calcareous sponges, gor- 

 gonians, and holothurians. 



A glance at the maps shows the close correlation between the bottom 

 deposits and the topographic features in the Castle Harbor and St. 

 George's Harbor regions. In Castle Harbor we find a large body of 

 water, of moderate and fairly uniform depth, in rather free communica- 

 tion on two sides with the sea, and with a free circulation of water, 

 though without strong tidal currents. Uiuler these favorable conditions 

 there is a considerable development of stony corals, gorgonians, and 

 millepores ; moUusks, worms, aud echinoderms also flourish in great 



