THE PELAGIC FAUNA AND FLORA. 209 
long trains or patches of a dirty yellow color. Dr. Farlow has 
identified as the same alga the pelagic plant found on one 
occasion north of Cape Hatteras, tinting the surface of the sea 
a dirty yellow for an area of about a quarter of a mile in length 
Fig. 133. —'Trichodesmium Fig. 134. — Coecosphere. Fig. 185. — Rhabdosphere. 
erythreum. $. $99. (Chall.) 10, (Chall.) 
by a hundred yards in width. This pelagic alga has been aptly 
described as resembling minute sheaves and bundles of chopped 
hay. Coccospheres (Fig. 134) and rhabdospheres (Fig. 135) 
are calcareous pelagic surface organisms, of which the tests 
and fragments, coccoliths and rhabdoliths, occur in numbers in 
globigerina ooze. They have been studied by the naturalists of 
the * Challenger," and Thomson regards them as calcareous 
alow of a peculiar form. They are found in abundance in the 
stomachs of Salpz. 
In addition to these smaller algz, which are indeed the true 
inhabitants of the surface, and flourish equally well in all parts 
of the ocean, —in the central parts of the Gulf of Mexico, along 
the Atlantic coast of the United States, or on the west coast of 
South America, — we find some of the higher algæ, but these 
are eonfined to very much more limited areas. Sir Joseph 
Hooker has described the giant kelp in the floating condition 
in which it ranges over a wide extent of the Southern Ocean. 
A similar species of kelp occurs in the Gulf of Georgia, where 
it serves as a refuge to a host of marine animals, which are 
sheltered within the comparatively quiet area occupied by it. 
Both in the Atlantic and Pacific, large tracts are covered by 
a species of Sargassum (Fig. 136), which in the Atlantic has 
given its name to the area known as the Sargasso Sea. 
1 The Sargasso Seais an immense body with a thickness of 300 fathoms, the sur- 
of warm water of 1,000 miles in diameter, face temperature of 22° C., diminishing 
