SEA-FLOOR DEPOSITS. PART I 337 



Station WS 479. 15. xi. 29. Lat. 62 32}' S. Long. 57° 55' W. 1523 m. (Plate XX.) 

 Diatomaceous MUD. This dark grey mud consists mainly of diatom frustules together with 

 flocculent aggregates of organic debris; many of the frustules retain their protoplasmic content. 

 Coscinodiscus, Thalassiosira, Cocconeis, Fragilaria, Corethron and Rhizosolenia are the chief genera. 

 Mineral grains are comparatively rare in occurrence and small in size, being mostly less than o-oi mm. 

 in diameter, though some are o- 1 mm. across ; most of them are angular fragments of quartz, but green 

 hornblende also is noted. 



Station WS 480. 16. xi. 29. Lat. 62 51 i' S. Long. 57 47J' W. 740 m. (Plate XX.) 

 Diatomaceous mud. The sample of greenish mud contains well- developed diatom frustules in fair 

 abundance and variety. Coscinodiscus, which preponderates among the centric forms, is associated 

 with Thalassiosira, Biddulphia and Cocconeis, while Rhizosolenia, Corethron and Fragilaria represent 

 the elongate and pennate forms repectively. Mineral grains occur in fair quantity, mostly angular or 

 subangular in shape, and usually less than o- 1 mm. in diameter ; quartz, green hornblende and volcanic 

 glass are noted. 



Station WS 481. 16. xi. 29. Lat. 62 59' S. Long. 57° 28' W. 453 m. (Plate XX.) 

 Sand. The bulk of this sample consists of mineral grains which range from a diameter of about 

 0-5 mm. to exceedingly small dimensions. Quartz, felspar, green hornblende, white mica and vol- 

 canic glass are the most prominent constituents. Among the organic constituents are Polyzoa, 

 Foraminifera and sponge spicules. The supernatant material forms flocculent aggregates which 

 enclose and buoy up diatoms and small mineral grains. The diatom genera include Coscinodiscus, 

 Triceratium, Thalassiosira and Grammatophora. 

 Station WS 482. 16. xi. 29. Lat. 63 10' S. Long. 57 i6|' W. 152 m. (Plate XX.) 

 Diatomaceous mud. The deposit has settled in layers during storage ; the top layer is a fine-grained 

 greenish mud, the lower portion is darker in colour (almost black) and coarser in grain. The two 

 fractions are approximately equal in bulk. The finer material consists largely of diatom debris, often 

 forming flocculent aggregates in which small angular mineral grains (mostly less than 001 mm. in 

 diameter) are enclosed. A considerable number of entire diatom frustules occur, among which 

 specimens of Triceratiutn are conspicuous by their size (0-5 mm. across); they are associated with 

 species of Coscinodiscus, Thalassiosira, Cocconeis, Fragilaria and Grammatophora. Some of the 

 frustules still have their cell contents, and the preserving liquid has a green tinge. Monaxid and 

 tetraxid sponge spicules are present. In the coarser material, mineral grains reach a diameter of 

 0-5 mm. but the average size is about 0-2 mm. ; the grains are chiefly angular to subangular. The 

 chief constituents are quartz, green hornblende and volcanic glass. While the proportion of sandy 

 material is considerable, character is given to the deposit by the diatoms ; hence it is classed as a 

 diatomaceous mud. 



Station WS 483. 21. xi. 29. Lat. 62 46! ' S. Long. 59 37-^ W. 1420 m. (Plate XX.) 

 Diatomaceous mud. This grey-green mud consists largely of flocculent aggregates formed of 

 diatom debris and enclosing a quantity of mineral grains which are usually less than 0-05 mm. in 

 diameter. Entire frustules of Corethron, Coscinodiscus, Cocconeis, Fragilaria, Biddulphia, Rhizoso- 

 lenia and Thalassiosira are noted, the first named being particularly abundant. The chief mineral 

 constituents are quartz, green hornblende and volcanic glass, splinters of the latter being especially 

 prominent. 



Station WS 484. 21. xi. 29. Lat. 62 54' S. Long. 59 28' W. 1008 m. (Plate XX.) 

 Diatomaceous mud. This green mud is eminently typical of its class. Frustules of Coscinodiscus, 

 Cocconeis, Fragilaria Rhizosolenia and Corethron occur in an undamaged condition, and also in all 

 stages of fragmentation. The flocculent aggregates which compose the bulk of the deposit enclose 

 angular mineral grains which are usually less than 0-05 mm. in diameter, but the size ranges up to 

 about o-i mm. Angular fragments of volcanic glass are conspicuous, along with grains of quartz, 

 green hornblende and white mica, in the mineral fraction. 



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