16 THE DEPTH AND MARINE DEPOSITS OF THE PACIPIC OCEAN. 



dant on the bottom, as well as in the mud of the manganese nodules, though 

 among the nodules it was not uncommon to find an occasional Bilocnlina. 

 Many of the dead radiolarians found on the bottom were obtained from the 

 guts of Salpae swimming near the surface or within the 300-fathom line in 

 the tow-nets sent to that depth. The same is the case with many of the 

 Dinoflagellata which have be^n considered as deep-sea types. . . . 



" The samples of the bottom obtained by the soundings taken by the 

 expedition or gathered in the mud-bag and in the trawl indicate that an 

 immense area of the bottom of the Eastern Pacific is covered with manga- 

 nese nodules, and that they play an important part in determining the 

 character of the bottom, not only in the area covered by this expedition but 

 also in other oceanic regions ; the Eastern Pacific area of manganese nodules 

 probably extends to the northwest of our lines to join the stations where 

 manganese nodules were found by the ' Albatross ' in 1899 in the Moser 

 Basin, on the line, San Francisco to Marquesas (PL 3). 



" This area may also extend south of our lines, Callao to Easter Island, 

 and join the line west of Valparaiso where the ' Challenger ' obtained man- 

 ganese nodules at many stations. I do not mean to imply that manganese 

 nodules are present to the exclusion of radiolarians and of globigerina3. It 

 is probable that the layer of nodules is partly covered by them, and by the 

 thick, sticky, dark chocolate-colored mud which is found wherever manganese 

 nodules occur. . . . 



" The Salpte guts gave us, in addition to the finer tow-nets, immense col- 

 lections of radiolarians, diatoms, and dinoflagellata, many of which have 

 been considered to live at great depth and upon the bottom. It is most 

 interesting to note the number of diatoms found in this tropical region. 

 They have usually been considered as characteristic of more temperate and 

 colder regions. On several occasions the surface waters were greatly dis- 

 colored by their presence, and the extent of their influence on the bottom 

 deposits is shown by the discovery of a number of localities where the 

 bottom samples at depths from 1490 to 2845 fathoms, in the track of the 

 great Peruvian current, formed a true infusorial earth." 



After these interesting extracts, giving details of the observations made 

 on board ship during the various cruises, we may now proceed to a detailed 

 description of the samples of these deposits which were sent to us for 

 examination. 



