284 
THE VOYAGE OF H.M.S. CHALLENGER. 
Fio. 30 . — Ttiscarora belknapi, Murray 
(one of the Phoeodaria). North 
Pacific, 500 fathoms. 
The species of Racliolaria are most abundant in tropical waters of rather low salinity, 
especially in the western and central Pacific and eastern Indian Oceans. In the 
Diatom Ooze at Station 157, in 1950 fathoms, lat. 53° 55' S., 84 species of Radiolaria 
have been recognised, while in the Radiolarian Ooze at Station 225, in 4475 fathoms, 
lat. 11° 24' N., 338 species have been found, and of these only six species are common 
to the two stations, two belonging 
to the order Spheeroidea, three 
to the Discoidea, and one to the 
Cyrtoidea. The results of numer- 
ous tow-net experiments appear 
to show that the Pheeodaria, and 
many of the Nassellaria, live in 
deep water, at a temperature as 
low as 40° F. In a Radiolarian 
Ooze the percentage of Radiolaria 
may be as high as 60 or 70 per 
Fio. 31. — Challengeria naresii, Mnnay . . 
(one of the Phaeodaria). North Cent., and in a Diatom Ooze OP 
Pacific, 500 fathoms. i-i. ~i n 
Globigenna Ooze, as high as 10 
per cent., but generally the percentage is very much less. In terrigenous deposits the 
Radiolarian remains seldom make up over 2 or 3 per cent, of the whole deposit. 
Sponge Spicules. — The spicules of siliceous Sponges are universally distributed in the 
different kinds of deep-sea deposits, the Hexactinellid spicules prevaihng in deep water 
and the Tetractinellid and Monaxonid spicules in the shallower depths. In some regions 
siliceous Sponges were dredged in great numbers, for instance, off Kerguelen, in 120 
fathoms, over one hundred specimens of Rossella antarctica w’ere obtained in ’one 
haul of the trawl ; at Zebu, Philippines, numerous specimens of Euplectella and other 
Sponges were obtained in 100 fathoms ; off the Ki Islands, in 129 fathoms, there were 
eighteen species of Hexactinellida and a large number of individuals ; in the Atlantic 
near the Cape Verdes there was procured in 1525 fathoms a large specimen of Poliopogon 
amrxdou (2x2 feet), attached to the branches of an Alcyonarian Coral ; off the Kermadecs, 
in 630 fathoms, there was obtained another Poliopogon {Poliopogon gigas), measuring 
3^x2 feet, which was but a fragment of what appeared to be an enormous Sponge ; in 
the Faroe Channel a large number of specimens of Pheronema {Holtenia) were dredged 
from a depth of 530 fathoms by the “ Porcupine.” In the deposits from areas like the 
above, where these silieeous Sponges flourish in large numbers, the spicules are particu- 
larly abundant, and make up a large proportion of some specimens of the deposit. With 
the exception, however, of the samples obtained from among these patches, terrigenous 
or pelagic deposits do not as a rule contain a large percentage of Sponge spicules, the 
average proportion in any of the types of deep-sea deposits not exceeding 2 or 3 per 
