3 2o DISCOVERY REPORTS 



Station 145. 7. i. 27. Stromness Harbour, South Georgia; between Grass Island and Tonsberg 

 Point. 26-35 m. (Plate XIX, inset.) 



Diatomaceous mud. The coarser constituents include a variety of diatoms, chiefly Coscinodiscus 

 (up to 0-2 mm. in diameter), Fragilaria, Cocconeis and Licmophora with occasional examples of 

 Pleurostgma. Simple and branched sponge spicules, amphipod fragments and sea-weeds were also 

 noted. Mineral grains, mainly quartz fragments, reach 0-2 mm. in diameter, but the average size is 

 much smaller. The finest material consists of mineral particles together with comminuted diatoms, 

 and other organic debris. 



Station 151. 16. i. 27. Lat. 53 25' S. Long. 35 15' W. 3200 m. (Plate XIX.) 

 Diatomaceous mud. The organic constituent is almost entirely diatomaceous, frustules of 

 Coscinodiscus, Fragilaria and Thalassiothrix being abundantly represented. Occasionally Radiolaria 

 and sponge spicules are seen. Mineral grains up to o-2 mm. in diameter occur in some quantity ; the 

 size of the grains is larger than would be expected at this depth and locality. 



Station 157. 20. i. 27. Lat. 53 51' S. Long. 36 11' 15" W. 970 m. (Plate XIX, inset.) 

 Diatomaceous mud. Stones are reported for this deposit in the Station List but none is present 

 in the small sample. The organic constituents consist of the usual diatomaceous assemblage 

 (Coscinodiscus, Fragilaria and Thalassiothrix) together with sponge spicules. The numerous mineral 

 grains are rounded and subangular in shape, and reach 0-2 mm. in diameter. 



Station 160. 7. ii. 27. Lat. 53°43'4o" S. Long. 40 57' W, near Shag Rocks. 177 m. (Plate XVII.) 

 Sand. This is a very " mixed " deposit, described in the official Station List as " Grey mud with 

 stones and rock ". One stone, 8 mm. in diameter, is present in the small sample available. The de- 

 posit consists of mineral grains and rock fragments up to 1 mm. in diameter, Globigerina and other 

 Foraminifera, together with exceedingly fine-grained, supernatant material which includes the 

 diatoms, Coscinodiscus, T/ialassiosira, Fragilaria, Rkizosolenia. 



Station 162. 17. ii. 27. Lat. 6o° 48' S. Long. 46 08' W. 320 m. (Plate XVII.) 

 Diatomaceous mud. A sample obtained off Signy Island, South Orkneys, and described as "green 

 mud " in the official Station List. The sediment is composed largely of fine-grained material which 

 appears to be comminuted diatoms, and there are many whole frustules of Coscinodiscus, Fragilaria 

 and Rhizosolenia. Mineral grains are generally less than 0-05 mm. in diameter and most of them are 

 angular fragments of quartz, but prismatic grains of green hornblende and flakes of white mica also 

 occur. 



Station 167. 20. ii. 27. Lat. 6o° 50' 30" S. Long. 46 15' W. 244-344 m. (Plate XVII.) 

 Diatomaceous mud. A fine-grained sediment consisting largely of mineral grains, only a few of 

 which attain a diameter of 0-2 mm. Quartz, hornblende and white mica are noted. Some sponge 

 spicules are present, and also frustules of Coscinodiscus and Fragilaria. The finer fraction of the sedi- 

 ment appears to consist of comminuted diatom frustules. 



Station 169. 22. ii. 27. Lat. 6o° 48' 50" S. Long. 5 1° 00' 20" W. 2514 m. (Plate XVII.) 

 Diatomaceous mud. The sample consists of two sections of core, in all about 40 cm. long. Various 

 parts of the core have been examined microscopically, but no appreciable differences have been 

 detected throughout its length. This dark, greenish grey mud consists essentially of diatom frustules 

 in considerable variety. Centric forms, especially Coscinodiscus and Thalassiosira, are conspicuous 

 by their size and abundance, while Biddulp/iia is less numerous ; navicular genera are represented by 

 Fragilaria and Achnanthes; and among elongate forms, Rhizosolenia is both abundant and well- 

 developed, while Corethron is smaller and less plentiful. There is a quantity of comminuted frustules, 

 the particles of which adhere and form flocculent groups. Mineral grains are present in fair quantity, 

 and reach a diameter of about 01 mm. They include grains of quartz and green hornblende and 

 flakes of white mica. The deposit might almost be called a diatom ooze, but the proportion of mineral 

 grains, though not great, is a real distinction between this sample and that from St. 12, for instance. 



