SYSTEMATIC ACCOUNT 345 



their characteristics are subject to so much variation that I am unable to distinguish 

 more than a very few well defined forms." The slide collection of F. W. Payne, now in 

 the British Museum (Nat. Hist.), contains what is to my mind the most perfect selection 

 of specimens of Navicula lyra it is possible to see. A close study of these most beautiful 

 mounts forces one to the conclusions of Cleve and Mann. I feel that in dealing with this 

 species the multiplication of varieties and forms serves no useful purpose, and that we 

 are called upon to regard the problem from a wider aspect. The species must be re- 

 garded as a polyphasic system, expressing itself in space and time. 



The species was observed in small numbers at one station only. The specimens closely 

 approximate to the type illustrated by Ehrenberg. 



Observed at St. WS 622. 



Navicula subpolaris Hendey, nom. nov. 



Navicula cristata, Peragallo, M. 1921, p. 56, pi. 2, fig. 11. 



Cells usually solitary. Valves linear-lanceolate in outline, angles acute. Valve surface 

 convex, possessing a prominent median raphe and a small and almost circular hyaline 

 central area ; polar and central nodules small. Valve surface furnished with strong trans- 

 verse striation. Upon either side of the raphe, between it and the margin of the valve, 

 is a fine line which extends to the apices of the cell. 



A small characteristic Antarctic diatom observed in small numbers in water obtained 

 from melted ice. The new name given above is necessary because Navicula cristata is 

 preoccupied (Navicula cristata Ehrenberg, 1854). 



Observed near St. 560. 



Navicula membranacea Cleve. (PI. XI, fig. 4.) 



Cleve, 1897 a, p. 24, pi. 2, figs. 25-28. 

 Lebour, 1930, p. 206, fig. 169. 



Cells united to form short, thick, straight chains. Cells in valve view narrow, linear, 

 with weak median inflation; apices pointed. Connective zone deep, giving the cell a 

 rectangular girdle view; zone finely striate, striae difficult to see. Chromatophores : 

 two undulating ribbon-like bodies, arranged in the apical axis of the cell. Apical axis of 

 cell 60-84/^. ; pervalvar axis 30-40/n. 



This weakly siliceous form, is common in the plankton of temperate and subtropical 

 seas. It was observed, but not in great numbers, to the south of Africa. 



Observed at St. 1373. 



Navicula Schuettii Van Heurck. 



Van Heurck, 1909, p. 13, pi. 1, fig. 10. 

 Valve broadly lanceolate, subrhomboidal, with subconical obtuse apices. Raphe 

 strong, straight; polar nodules prominent but small; central nodules small, surrounded 

 by a small rounded or oval central area ; axial area narrow. Valve surface covered with a 

 fine moniliform striation arranged somewhat radially. Striae of the median portion of 

 the valve more distant than those which occupy the remainder of the valve surface. 



