180 
THE VOYAGE OF H.M.S. CHALLENGER. 
to 25 per cent, of carbonate of lime, derived from coral debris, fragments of Pteropods, 
Gasterojiods, Coccolitlis, with pelagic and other Foraminifera. The mass of the deposits 
was formed of fine mineral fragments (see Chart 39). 
Tahiti to Valparaiso. — As might be expected from the undulating nature of the 
bottom, and the varying distance from land, the deposits presented considerable variety 
during the trip between Tahiti and Valparaiso (see Chart 38). In all depths less than 
2000 fathoms the deposit was a Globigerina Ooze with over 50 per cent, of carbonate of 
lime, the highest percentage being 84 in IGOO fathoms. As the 40th parallel south was 
approached the purely tropical species of pelagic Foraminifera — such as Globigerina con- 
globata, Splueroidina dehiscens, Pulvimdina tumida, Pullenia obliquiloculata — disap- 
peared both from the surface waters and from the deposits at the bottom. At the depth 
of IGOO fathoms above referred to the deposit was chiefly composed of the following 
species, which were mostly dwarfed : — Globigemna buUoides, Globigerina injlata, Globi- 
gerina dubia, Globigerina sequilateralis, Orbulina universa, Pulvinulina canariensis, 
Pidvinulina micheliniana, and Pulvinulina menardii. There were a few fragments of 
Pteropods in the deposit from 1500 fathoms, but with this exception the shells of pelagic 
Mollusca were entirely removed from the bottom. 
In depths greater than 2000 fathoms there was less than 50 per cent, of carbonate of 
lime, viz., 4G per cent, at 2075 fathoms, 2G per cent, at 2375 fathoms, still less in 2400 
fathoms, and scarcely a trace in 2G00 fathoms, thus showing a gradual diminution in the 
number of calcareous shells with increasing depth (see Diagrams 19, 20, and 21). 
At several stations the sounding tube had penetrated over a foot into the deposit, 
and on two occasions, viz., at 2075 and 2270 fathoms, there was much less carbonate 
of lime in the lower layers than in the upper ones ; but on another occasion, in 2335 
fathoms, the arrangement was the reverse of this, a Red Clay with only a few calcareous 
shells occupying the surface, and a Globigerina Ooze with very many calcareous shells 
forming the deeper layers. There were very few remains of siliceous organisms in all 
the.se deposits, in which respect they are in marked contrast to the deposits of the Central 
and West Pacific. 
The deposits in 2225 fathoms (see Chart 38) and 21G0 fathoms off the coast of South 
America (.see Chart 40) were Blue I\Iuds, similar in all essential respects. The former 
contained G, the latter 15, per cent, of carbonate of lime, which con.sisted chiefly of the 
shells of Glolngerina and Orbidina and Coccolitlis. The mineral particles consisted of 
cjuartz, mica, felspars, augite, hornblende, palagonite, and glauconite. It is worthy of 
note that glauconite was not ob.served in the deposits after leaving the coast of Jajian till 
approaching Val[»nraiso, in 2225 fathoms, and with some exceptions the same remark 
applies to quartz grains. The trawlings on both occasions were very productive, some 
pumice stones and a few manganese nodules being obtained from 21G0 fathoms. At 41 
fathoms a Blue Mud was obtained, containing only a trace of carbonate of lime, in which 
