SEA-FLOOR DEPOSITS. PART I 315 



Station 19. 4. iii. 26. 10 miles N 39 E of Cape Saunders, South Georgia. 200 m. (Plate XIX, 

 inset.) 



Diatomaceous mud. This dark, greenish sandy sediment approaches a diatom ooze in the 

 abundance of diatoms. Coscinodiscus is the most conspicuous genus, but valves of Fragilaria are 

 also present with occasional sponge spicules and radiolarian fragments. Quartz grains reach 0-2 mm. 

 in diameter, and prisms of green hornblende 0-15 mm. in length, but most of the grains are smaller. 

 Some amount of greenish flocculent material is present. 



Station 20. 4. iii. 26. 14-6 miles N 41° E of Cape Saunders, South Georgia. 210 m. (Plate XIX, 

 inset.) 



Diatomaceous mud. This sediment is fine-grained and greenish grey in colour. The bulk of the 

 sample consists of diatoms {Coscinodiscus, Fragilaria and other forms) and exceedingly fine particles 

 of comminuted diatoms. Mineral grains include quartz (up to 0-2 mm., abundant) and green horn- 

 blende (o-i mm.). Sponge spicules also occur. The greenish colour of the sediment is probably due 

 to chlorophyll or other pigment of the diatoms, for the preservative liquid has acquired a green 

 colour. 



Station 23. 14. iii. 26. 5-3 miles N 44 E of Merton Rock, South Georgia. 228 m. (Plate XIX, 

 inset.) 



Diatomaceous mud. This greenish grey "buttery" deposit contains much detrital material, 

 chiefly subangular quartz grains which range down from a diameter of about 0-05 mm. to exceedingly 

 small particles. Flakes of white mica, however, attain a diameter up to o-i mm. The organic material 

 is chiefly diatomaceous. Frustules of Coscinodiscus are large and abundant; they are accompanied by 

 Fragilaria, Thalassiosira and other forms. Some sponge spicules are noted. The greenish hue is 

 thought to be due to vegetable pigments. 



Station 28. 16. iii. 26. West Cumberland Bay, South Georgia. 3-3 miles S 45 W of Jason Light. 

 Two samples from depths of 65 and 168 m. respectively. (Plate XIX, inset.) 



Terrigenous mud. (a) The sample from 65 m. is a grey mud formed of exceedingly fine mineral 

 particles which react to polarized light. There is a fair quantity of subangular detrital grains and 

 centric diatoms which reach a diameter of o-i mm. 



(6) The sample from 168 m. is a black mud, microscopically similar to sample (a), but yellow oil 

 globules are commonly seen. Apart from the diatoms the material is remarkably like some of the 

 black muds of the Mersey estuary in England. 



Station 29. 16. iii. 26. West Cumberland Bay, South Georgia. 5-9 miles Ssi°W of Jason 

 Light. 23 m. (Plate XIX, inset.) 



Terrigenous mud. A sediment of "buttery" consistency. The top layers of the sample have 

 oxidized slightly, giving a yellowish tinge. Though some particles reach a diameter of o-i mm., the 

 bulk of the material is extremely fine-grained, most of the particles being below o-oi mm. in diameter. 

 Some of the fine particles react to polarized light, others appear not to do so. No organic material 

 was recognized definitely. 



Station 30. 16. iii. 26. West Cumberland Bay, South Georgia. 2-8 miles S 24 W of Jason 

 Light. 251 m. (Plate XIX, inset.) 



Terrigenous mud. Similar to sample from St. 29 in general constitution, but perhaps more of the 

 coarser particles. Some small frustules of Coscinodiscus from o-oi to 0-05 mm. in diameter are noted. 



Station 31. 17. iii. 26. 13-5 miles N 89 E of Jason Light, South Georgia. 220 m. (Plate XIX, 

 inset.) 



Diatomaceous mud. The bulk of the sample consists of diatomaceous remains, mostly com- 

 minuted, but containing some frustules of Coscinodiscus, Fragilaria and Thalassiothrix. The centric 

 forms are often fairly large, but much of the comminuted material is below o-oi mm. in diameter. 

 Sponge spicules and green filamentous algae are also present. Many quartz grains reach a diameter 



