230 GENERAL GEOLOGY 



amount of organic material to the bottoms of the lakes, which gradually passes into 

 a type of peat. The individual plant organisms were often of a large size, at least 

 2 to 3 feet in diameter, with a depth of approximately equal amount. 



Diatoms abounded in all the lakes in the neighbourhood of Cape Boyds, and 

 contributed largely to form muds on the lake bottoms. A large triangular diatom, 

 apparently allied to Triceratium, was specially abundant in the muds of Clear Lake. 

 In the neighbourhood of the Ross Barrier ice-cliff the waters of Ross Sea for a con- 

 siderable distance to the north of the ice-cliff were observed by us to be olive-green 

 from the abiuidance of diatoms. R. N. Rudmose Brown states that Dr. W. S. Bruce 

 has observed the same thing in the sea water off Louis Philippe Land.* 



ANIMALS 



Foraminifera. Foraminifera evidently abound in Antarctic seas. A later chapter 

 of this Report by Mr. F. Chapman describes the varieties met with in the raised 

 marine deposits of Ross Island and of South Victoria Land. In the case of the 

 raised marine deposit near Mount Larsen, the well-known genus Biloculina was so 

 abundant as almost to constitute Biloculina clays, like those so well known in the 

 neighbourhood of the Arctic Circle. 



SjMnges. Sponges were wonderfully abundant, so much so as to be quite 

 important contributors to the muds and oozes forming at present at the bottom of 

 McMurdo Sound and Ross Sea. Certainly a considerable portion of the floor of 

 McMurdo Sound must be almost as white as snow, owing to the presence of a 

 continuous deposit of siliceous sponge spicules, derived from the breaking up of 

 sponge stocks. Such spicules must be intermixed with boulders, rock dust, and 

 fragments of angular felspar, dumped by floating ice floes or by ice bergs. These 

 siliceous sponges frequently attain a very large size, of from a foot to li feet in 

 diameter. 



Corals. Only one variety of coral was observed by us, the specimen discovered 

 by Mackay in the upthrust marine muds near the foot of Backstairs Passage, 

 in the Drygalskl region. This is a solitary type of coral, and has already been 

 figured in "The Heart of the Antarctic," vol. ii., Plate facing p. 320. No living 

 specimens of coral were obtained by means of dredging. The specimen just referred 

 to was found in the upthrust muds which there overlie some very old glacier ice. 



Echinoderms. Echinoderms were extraordinarily abundant. On looking 

 through the clear ice one could see that the sea bottom was almost completely 

 covered in places with echini. They, too, must form no unimportant contribution 

 to the marine deposits now forming in McMurdo Sound. These seas also abound 



* Scientific Results of the Scottish National Antarctic Expedition, vol. iii. p. 13. The Problems 

 of Antarctic Plant Life. By R. N. Rudmose Brown, D.Sc. The Scottish Oceanographical Laboratory, 

 Edinbm-gh, 1912. 



