SEA-FLOOR DEPOSITS. PART I 323 



0-25 mm., and the average size is estimated at about 005 mm. Centric diatoms, Coscinodiscas and 

 Thalassiosira, reach o-i mm. in diameter, while Cocconeis and Fragilaria are also well developed. 

 These forms occur with sponge spicules in the flocculent material which, however, appears to be less 

 in proportionate bulk than in the preceding samples (Sts. 197, 198 and 199). 



Station 201. 5. iv. 27. Lat. 63 00' 30" S. Long. 59 06' 30" W. Bransfield Strait, South Shet- 

 lands. 343 m. (Plate XX.) 



Diatomaceous mud. This small sample contains numerous grains of quartz and green horn- 

 blende, the average diameter of which is probably between o-i and 0-05 mm. Angular fragments of 

 vesicular volcanic glass are also conspicuous. The grains are held in flocculent material composed 

 of diatom tests (whole and fragmentary) and organic debris, of which some at least consists of the 

 protoplasmic constituent of the diatoms. 



Station 202. 5. iv. 27. Lat. 62 48' S. Long. 6o°05'W. Bransfield Strait, South Shetlands. 

 909 m. (Plate XX.) 



Diatomaceous mud. A considerable proportion of this dark grey mud consists of detrital grains, 

 angular to rounded in shape; some of the grains are more than o-i mm. in diameter, but also there 

 are many more whose diameter is less than 0-02 mm. Fragments of volcanic glass are sharply angular 

 while quartz grains are usually more rounded. Flocculent material is composed largely of tiny 

 mineral grains or rods, with some fragmentary diatom frustules. The genera Coscinodiscus, Thalas- 

 siosira, Cocconeis, Fragilaria and Rhizosolenia are present but not abundant. 



Station 203. 5-6. iv. 27. Lat. 62° 56' S. Long. 59 50' W. Bransfield Strait, South Shetlands. 

 949 m. (Plate XX.) 



Diatomaceous mud. A brownish mud with a conspicuous proportion of detrital grains, some of 

 which reach a diameter of 0-25 mm. Green hornblende and brown volcanic glass are noted in 

 addition to the predominant quartz. The fine-grained fraction, of the usual flocculent character, 

 includes tiny mineral fragments, sponge spicules, comminuted diatom frustules, and small diatoms 

 about 0-05 mm. in diameter. The genera Thalassiosira, Coscinodiscus, Cocconeis and Fragilaria are 

 represented. 



Station 204. 6. iv. 27. Lat. 63 05' S. Long. 59 42' W. Bransfield Strait, South Shetlands. 

 943 m. (Plate XX.) 



Diatomaceous mud. Similar in general character to the sample from St. 203. Some of this sedi- 

 ment was spread on a glass slip in a thick film of water; movement of the cover-glass caused groups 

 of sand grains to be rafted along on pieces of flocculent material which preserved their continuity. 



Station 206. 6. iv. 27. Lat. 63 26' S. Long. 59 28' W. Bransfield Strait, South Shetlands. 

 310 m. (Plate XX.) 



Diatomaceous mud. This is essentially similar to the sample from St. 204, consisting mainly of 

 flocculent material which encloses diatom frustules and mineral grains. The latter are usually very 

 small, but there are larger grains (up to o-i mm. diameter) of quartz, volcanic glass and green 

 hornblende. The diatoms include representatives of the genera Coscinodiscus, Thalassiosira, Cocconeis, 

 Fragilaria. 



Station 209. 14. iv. 27. Port Foster, Deception Island, South Shetlands. 168 m. (Plate XX.) 



Terrigenous mud. The mineral fraction consists mainly of angular fragments of brown, vesicular, 

 volcanic glass which vary in size between a diameter of about 0-2 mm. and exceedingly small di- 

 mensions. Some flocculent matter is present, with the diatoms Thalassiosira, Cocconeis, Licmophora 

 and Fragilaria, but unbroken frustules are not abundant. The flocculent material causes agglutination 

 so that the deposit forms a coherent mass on drying. 



Station 211. 15. iv. 27. Lat. 62 35' S. Long. 63 ° 20' W. 2865 m. (Plate XX.) 

 Diatomaceous mud. A brown-grey mud containing abundant mineral grains which are usually 

 less than 0-05 mm. in diameter. The grains are mainly of quartz, but occasional fragments of green 



