4 MUSEUM, BROOKLYN INSTITUTE OF ARTS AND SCIENCES. 
and their local fauna is not reinforced by creatures characteristic of the 
current. It is interesting to observe, however, that at the Tortugas we find 
more than a mere concentration of individuals, for a number of characteris- 
tic species appear to be confined to this region alone. 
Moreover, at the Tortugas we have a small land mass surrounded by 
pure, deep ocean water, while at the Bahamas we find vast areas of shallow 
flats, covered mainly with coralline mud. These great banks of the Bahamas 
are veritable submarine deserts, covered only with a sparse growth of coral- 
line, alga:*, and with hei-e and there a cluster of reef-corals and gorgonians. 
It is remarkable, also, that the water over these shallow banks is almost 
as deficient in life as is the desert bottom itself. Almost no Sagitta^, Salpae 
or Crustacea being found, and among Medusa3 only Olindias, Cubaia, and 
Lymnorea are abundant. 
Indeed, the water over the banks is usually charged with a flocculent 
mass of silt, which readily adheres to pelagic animals, and appears to be ra- 
pidly fatal to them. Only in this manner can we account for the poverty of 
pelagic life over the Bahama banks, for the deep-water regions of the Baha- 
mas, such as the Tongue of the Ocean or the area to the eastward of Great 
Abaco Island, are rich in pelagic animals, which appear to be free from silt 
and in excellent condition. The water from the deep areas must, however, 
often be driven over the shallow banks and its life destroyed. 
The coral reefs of the Bahamas are richer in species than are those of 
the Tortugas. They are best developed along the windward edges of the 
banks, the richest single reef being probably that which extends along almost 
the entire eastern shore of the Andros Islands, about one mile out from the 
beach. On the other hand fewer species of marine invertebrates and fishes 
are found among the Bahama reefs than among those of the Tortugas. The 
actual area occupied by corals is insignificant in comparison with the great 
extent of barren flats around them. 
In general it appears that while tlie Tortugas fauna is recruited from the 
pelagic life of the Gulf Stream, and from the drift caused by prevailing 
winds, the Bahama fauna is depleted by the same winds, and is poor in those 
creatures which are mainly dependent upon great currents for their distri- 
bution. 
Morphology, etc. A unique opportunity was afforded for the study of the 
post-embryonic development of Cubaia, and Olindias, and it appears that 
