34(5 DK MURRAY ON THE DEEP AND SHALLOW-WATER MARINE FAUNA 



soundings were situated towards the Antarctic Circle. Three other soundings greater than 

 1000 fathoms are recorded to the south of the 60th parallel of south latitude. Ross obtained 

 many soundings in depths ranging from 190 to over 600 fathoms (347 to 1097 metres) 

 to the east of Victoria Land and off the Ice Barrier within the Antarctic Circle. Again, 

 in long. 15° W., within the Antarctic Circle, Ross paid out 4000 fathoms (7315 metres) 

 of line without reaching bottom, so that there is probably a great depth in this position. 

 Wilkes obtained depths of 800 and 500 fathoms (1463 and 914 metres) off Adelie Land. 



With the exception of several deep soundings where no bottom was found, this is all 

 we know about the depths in the Southern and Antarctic Oceans. The indications, on 

 the whole, point to a gradual shoaling of the sea-bed from the 40th parallel southwards 

 towards the shores of the Antarctic Continent, situated at some points close to the 

 Antarctic Circle, for instance at Wilkes Land. In some places, however, the sea-bed 

 rises into somewhat shallow plateaus, as around Kerguelen and other oceanic islands, and 

 in other places sinks to great depths, as in the Ross Deep and Barker Basin. 1 



Marine Deposits on the Sea-floor. — Nearly all the information we have as to the 

 deposits on the sea-bed near to or within the Antarctic Circle is derived from the 

 observations of the Challenger Expedition, together with a few additions from the Ross 

 and Wilkes Expeditions. At her most southerly soundings and dredgings the Challenger 

 procured a Blue Mud made up chiefly of detrital matter from the Antarctic Continent. 

 Imbedded in these muds were large and small fragments of granites, quartziferous 

 diorites, schistoid diorites, amphibolites, mica schists, grained quartzites, sandstones, 

 compact limestones, and partially decomposed earthy shales. These rock fragments 

 were evidently transported from the Antarctic Continent by the icebergs, and their 

 lithological character leaves no doubt that true continental land, and not a group of 

 volcanic islands, is situated within the Antarctic Circle. These rocks were most 

 abundant in the Challenger's dredgings on the Blue Mud at the most southerly 

 stations, but they were met with in diminished numbers in all the dredgings within 

 the area of the ocean affected at times by floating ice from the Antarctic Seas." 

 Although we have very few observations as to its geographical extension, still, judging 

 from what occurs off other continental shores, we may feel sure that the Blue Mud 

 extends all round the Antarctic Continent to a distance of about 200 miles (322 kilo- 

 metres) seawards. 



To the north of the Blue Mud the sea-floor is occupied by a white or cream-coloured 

 deposit chiefly made up of the silicious frustules of Diatoms, with a large admixture of 

 Radiolarians and Sponge spicules. In some places this Diatom Ooze extends north nearly 

 to the 40th parallel. But about the 50th parallel it appears to be usually replaced by a 



! See Charts in a Summary of the Scientific Results obtained at the sounding, dredging, and trawling Station* oi 

 H..M.S. Challenger, 1895. 



2 This view as to the origin of these continental rocks is supported by the facts that D'Urville found a rocky islet 

 off Adelie Land, to be composed of gneiss and granite, that Wilkes found, on an iceberg in the same locality, boulders 

 of red sandstone, and that Mr BoRCHOREYINK, who landed at Cape Adair from the whaler "Antarctic" in 1895, 

 brought away fragments of mica-schists and microcline-granite, with quartz, felspar, tourmaline, and garnets. 



