FRESHWATER ALU.E OK THE SOUTH ORKNEYS. 133 



64. NAVICULA MUTICOPSIS, Van Heurck, Diatomees, Result, voyage du s.y. 

 " Belgica," Anvers, 1909, p. 12, tub. 2, fig. 181 (text fig. 1, B, p. 122). 



Samples 8, 9, 10, 11, and 15, common ; previously recorded from the Antarctic 

 (Van Heurck, Messrs West). 



Length of valve = 21-24 M ; breadth (at widest point) = 10 /u. 



In most of the individuals the sides were quite fiat, but in others they were somewhat 

 arched ; ends pronouncedly swollen in a capitate manner. Such capitate forms 

 approach jV. dicephala (Ehrb.), W. Smith. 



65. ? NAVICULA LUCIDULA, Grun. Van Heurck, Atlas, 1880-81, pi. xiv., fig. 40. 

 Sample 9, rather rare. 



Certainly a very close ally of this species. 



66. NAVICULA MUTICA, Ktitz. ; Van Heurck, Syno2)sis Diat., 1885, p. 95, pi. x., 

 fig. 17. 



Samples 8, 9, 10, 13, and 17, common; previously recorded from the Antarctic 

 (Reiusch, Holmboe). 



Length of valve = 16-35 M ; breadth = 7-11 M (incl. f. Goppertiana, Bleisch). 



67. AMPHORA OVALIS, Kiitz. ; Van Heurck, Synopsis Diat., 1885, p. 59, pi. i., 

 fig. 1. 



Sample 4 (red snow !), isolated ; the var. gracilis has previously been recorded from 

 Kergueleu (Reiusch). 



68. GOMPHONEMA MONTANUM, Schum. ; Van Heurck, Synopsis Diat., 1885, p. 124, 

 pi. xxiii., figs. 33 and 36. 



Sample 9, isolated specimens. 



EXPLANATION OF THE PLATES. 



PLATE I. 



Fig. 1. Protoderma brownii, n. sp. A small portion of one of the sheets of cells formed by this species 

 ( x 830). 



Figs. 2-6. Chlorosphxra antarctica, n. sp. Fig. 2. Large isolated cell with a wide mucilage-sheath and 

 a quantity of fat in the cell-contents ( x 540). Fig. 3. A group of small cells without mucilage-sheath ; fat 

 equally diffused through the contents (xllOO). Figs. 4-5. Oval cells with segregated masses of fat; 

 possibly a stage in which the cells are preparing to divide (cf. p. 104) ( x 830, 730 respectively). Fig. 6. A 

 cell in which the fat is very prominently developed ( x 540). 



Figs. 7-11. Scotiella antarctica, n. sp. 1-2 = principal wings; 3-4 and 5-6 = the two pairs of lateral 

 wings; pw = principal wings. Fig. 7. A rather small normal individual, as seen when the principal wings 

 are parallel to the substratum ( x 830). Figs. 8, 9. Two oblique end-views of the organism to show the 

 course of the wings ( x 830). Fig. 10. Part of a normal individual in which the principal wings are inclined 

 to the substratum ( x 540). Fig. 11. An individual seen in optical section ( x 430). 



Figs. 12-16. Scotiella antarctica, n. sp. Stages in formation of resting-spores (1). Fig. 12. An 

 individual in which the wings have lost in definition ( x 540). Figs. 13, 14, 15. Three stages in the 



o *<V < 



I I R R A R Y 



