SUBMARINE DEPOSITS. 275 
most favorable conditions for their preservation, therefore, the 
fossils would give very imperfect evidence in regard to the 
variety of species which once constituted the fauna of any dis- 
trict. 
I quote from Murray and Pourtalés : — 
* Between Cape Hatteras and Lat. 31? 48' N., the deposits are green 
muds or sands. They are with two exceptions under 1,000 fathoms, 
and are mostly under the waters of the Gulf Stream, or along its inner 
margin. The mineral particles are much the same as those in the de- 
posits north of Cape Hatteras, but are all very much smaller, and have 
evidently not been transported by ice. The mineral particles, with the 
exception of the concretions formed at the bottom, seldom exceed 0.4 
mm. in diameter, and consist of quartz, feldspars, augite, hornblende, 
magnetite, and а few fragments of glassy rocks. Glauconitie grains 
and casts are frequently very abundant, as are also grains of manganese 
peroxide. 
“ The carbonate of lime makes up usually over fifty per cent of the 
whole deposit, and consists chiefly of the dead shells of pelagic and other 
foraminifera, along with shells of pelagic mollusks, fragments of echino- 
derms and polyzoa, ostracodes, and eoccoliths. АП the tropical species 
of pelagic foraminifera are abundant in these deposits, while they 
were relatively rare in the deposits along the coast to the north of Cape 
Hatteras. 
* The remains of siliceous organisms, as diatoms, radiolarians, sponge 
spicules, and glauconitic casts of foraminifera and other organisms, 
make up usually ten or twelve per cent of the deposit. 
“ The finer washings of these deposits are of a greenish color, which 
seems to be chiefly due to the presence of some amorphous organic sub- 
Stance, the nature of which has not yet been determined. A similar 
greenish matter was met with by the ‘Challenger’ in deposits from 
the same depths off the coasts of Africa, Australia, Japan, and China. 
These are the modern greensands and muds to which attention was first 
called by the late Professor Bailey. 
* Many of these deposits might equally well be called globigerina 
ooze. 
“ Phosphate of lime and manganese concretions are present in all 
the deposits, and one remarkable concretion is described in detail, from 
Station 31T,.in a depth of 333 fathoms, immediately under the waters 
of the Gulf Stream. The ground from which the coneretion was pro- 
Cured was hard, and it appears to have been formed in the position 
from which it was dredged. Its form was irregular, — the greatest 
and of a mottled black and brown 
diameter being about nine inches, 
