SUBMARINE DEPOSITS. 971 
ites, mica schists, serpentine rocks, and compact limestones. These 
fragments were not larger than six or seven centimetres in diameter. 
The ‘Blake,’ in 1,241 fathoms, and Lat. 39° 43! N., dredged large frag- 
ments of the same rocks, some of which were glaciated. In Lat. 41° 
14 N. and 1,340 fathoms the ‘Challenger’ again dredged similar rock 
fragments, and one block of syenite weighing five hundred-weight. 
These deposits being all within the influenee of the Labrador current, 
these rocks may be regarded as chiefly ice-borne. The mineral par- 
ticles and clayey matter usually make up from eighty to eighty-five 
per cent of the whole deposit. 
“ The carbonate of lime in these deposits varies from about three to 
eighteen per cent; it consists of coccoliths and coccospheres, of pelagic 
and other foraminifera, and of fragments of echinoderms, polyzoa, ostra- 
codes, and mollusks. The pelagic foraminifera shells and coceospheres 
are more abundant in the deeper deposits far from the land than in 
those from shallower water near the coast. 
“ The siliceous remains of diatoms, radiolarians, and sponges, to- 
gether with arenaceous foraminifera and glauconitic casts of calca- 
reous foraminifera, make up sometimes four or five per cent of the 
deposit. Mixed with the mud are also found pinnules of erinoids and 
otoliths of fishes." 
Mr. Pourtalés noticed, from his examination of the large col- 
lection of foraminifera brought together in the soundings made 
by officers of the Coast Survey, that off our Atlantic coasts cer- 
tain forms of foraminifera characterized distinct regions. 
“ The first, nearest the coast line, is marked by a great poverty of 
forms. Excepting a few small Polystomelle, we find nothing in the 
sand, which is kept in continual motion by the waves. This region 
may be considered to extend to a depth of ten or twelve fathoms. 
Farther seaward there are different species of Miliolinz, but not in 
large numbers. They extend to about forty fathoms, and also beyond, 
as 16 were sporadically. . . . 
“ From twenty-five to seventy fathoms Zruncatulina advena D'Orb. 
is the characteristic form. The next region, that of the larger Margi- 
nulinz and Cristellarize, encroaches on the first; it begins at a depth 
of about thirty-five fathoms, and extends one hundred fathoms be- 
yond. ... 
“From a depth of sixty fathoms the sand begins to be mixed with 
Globigerine, their numbers increasing so much with the depth that at 
1 The mineral particles consist of frag- hornblende, augite, mica, tourmaline, and 
ments of ancient rocks, quartz, mono- occasionally glauconitie grains. 
clinic and triclinic feldspars, magnetite, 
