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sharks; and just as the calcareous shells are eliminated in the 
depths, so all the remains of the larger vertebrates are absent except 
the most resistant portions. These bones often serve as a centre 
for the manganese-iron concretions, being frequently surrounded by 
layers several centimetres in thickness. In the same dredgings on 
the red clay areas, some sharks’ teeth and cetacean ear-bones, some 
of which belong to extinct species, are surrounded with thick 
layers of the manganese, and others with merely a slight coating. 
We will make use of these facts to establish the conclusions 
which terminate this paper. 
In these red clays there occur, in addition, the greatest number 
of cosmic metallic spherules, or chondres, the nature and characters 
of which we have pointed out elsewhere.* We merely indicate their 
presence here, as we will support our conclusions by a reference to 
their distribution. 
Reviewing, then, the distribution of oceanic deposits, we may 
summarise thus : — 
(1) The terrigenous deposits, the blue muds, green muds and 
sands, red muds, volcanic muds and sands, coral muds and sands, are 
met with in those regions of the ocean nearest to land. With the 
exception of the volcanic muds and sands, and coral muds and 
sands, around oceanic islands, these deposits are found only along 
the borders of continents and continental islands, and in enclosed 
and partially enclosed seas. 
(2) The organic oozes and red clay are confined to the abysmal 
regions of the ocean basins; a Pteropod ooze is met with in tropical 
and subtropical regions in depths less than 1500 fathoms, a 
Globigerina ooze in the same regions between the depths of 500 and 
2800 fathoms, a Radiolarian ooze in the central portions of the 
Pacific at depths greater than 2500 fathoms, a Diatom ooze in the 
Southern Ocean south of the latitude of 45° South, a red clay 
anywhere within the latitudes of 45° north and south at depths 
greater than 2200 fathoms. 
O 
Conclusions . — All the facts and details enumerated in the fore- 
going pages point to certain conclusions which are of considerable 
geological interest, and which appear to be warranted by the present 
state of our investigations. 
* “On Cosmic and Volcanic Dust,” Proc. Hoy. Soc. Edin., 1883-4. 
