72 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



of the line being covered "with manganese nodules on which were found 

 attached a few insignificant siliceous Sponges, an occasional Ophiuran, 

 and a few Brachiopods or diminutive worm tubes ; the same bottom con- 

 tinuing to Sala y Gomez and between it and Easter Island. Sala y 

 Gomez and Easter Island are connected by a ridge on which we found 

 1142 fathoms near Sala y Gomez, and 1696 fathoms between it and 

 Easter Island. The ridge rises rapidly from about 2000 fathoms, the 

 general oceanic depth within about 100 miles, to over 1100 fathoms 

 within a comparatively short distance from both Sala y Gomez and 

 Easter Island. 



The southern part of our line from Easter Island to the Galapagos 

 shows all the characteristic features of the western part of the line 

 from Callao to Easter Island : like it, as far as the 12th degree of south- 

 ern latitude, it proved comparatively barren, the bottom consisting of 

 manganese nodules to within about 250 miles of the Galapagos. The 

 pelagic and intermediate fauna from Easter Island to 12° south latitude 

 was very poor, and the serial temperatures show that we were outside 

 and to the westward of the great Humboldt current. But near the 12th 

 degree of southern latitude a sudden change took place ; the pelagic 

 and intermediate fauna became quite abundant again, and soon fully as 

 rich as at any time in the Humboldt current. There was also a marked 

 change in the temperature of the water as shown by the serials; show- 

 ing that from the 12th degree of southern latitude to the Galapagos we 

 were cutting across the western part of the Humboldt current. The 

 great changes of tempei'ature which took place in the layers of the water 

 between 50 and 300 fathoms are most striking, and show Avhat a disturb- 

 ing element the great mass of cold water flowing north must be in the 

 equatorial regions of the Panamic district to the south and to the north 

 of the Galapagos. South of the Galapagos the western flow of the 

 Humboldt current must be nearly 900 miles wide and of about the same 

 width when running parallel to the South American coast. 



The range of temperatures between 30 and 150 fathoms is at some 

 points as great as 21°. Such extremes cannot fail to aff'ect the dis- 

 tribution of the pelagic fauna, and may account for the mass of dead 

 material often collected in the intermediate tows when hauling at depths 

 of less than 300 fathoms, when the range becomes as great as 28°. Such 

 a range of temperature is far greater than that of the isochrymic lines 

 which separate coast fauual divisions. The bottom fauna, as we en- 

 tered the Humboldt current going north, gradually became richer in spite 

 of its being covered with manganese nodules. 



