577 



Very rare around the Færoes, only ;i few specimens occurred in 

 plankton Ironi March to September. Il seems to me as il' tliis boreal, 

 oceanic species which predominates in the [rminger-Sea has become 

 rarer in the eastern part of the North Atlantic Ocean during the lasl 

 live years Ihan it was before. 



ACHNANTHEAE. 

 XIX. ACHNANTHES Bory, 1822. 



52. A. taeniata Grun., K. Sv. Vet. Akad. Handl. 17, No. 2, 1880, 



p. 22, PI. I, fig. 5; Gran, Bibliotheca Botanica, 42, 1897, p. 8, PI. I, 



ligs.."), 10. 



A few specimens of a chain-forming diatom, probably .1. taeniata, were 

 found in plankton from March, Ma} r , July, August. Boreal-arctic, neritic 



species. 



NITZSCHIEAE. 

 XX. XITZSCHIA Hassall., 1845. 



53. N. seriata Cleve, Diat. of Vega, Vega-Exped. vetensk. iakt., 



PI. 38, fig. 75; N. fraudulenta Cleve, Fish. Board for Scotland, 1897, 



p. 300, PI. I, fig. 11. 



Found in the plankton from March to August, but mostly very 

 sparingly; it predominates in some samples of June 1898. Optimum of 

 temperature about 8° — 9° C. [See tables.] 



54. N. delicatissima Cleve, A Treatise on the Phytoplankton, 



1898, p. 24, PI. II, fig. 22. 



Found together with the above species in May— June of 1898, but 

 at the beginning of September is found by itself. Both species are boreal. 



II. Pterospermataceae. 



With regard to the algæ which I have named Pterosper- 

 mataceae, very little is known. They consist of a spherical (or 

 rarely, ovoid) eell furnished with wing4ists on the surface; the cell- 

 contents are of a brownish colour and eontain numerous small 

 drops of oil. The development of the cells is not known; Gran 

 (Das Plankton des norweg. Nordmeeres, p. 164) mentions that he 

 has found empty cells with an opening or scratch through which 

 the contents may have escaped , and I have also seen such speci- 

 mens. I can agree with him in his supposition thai il may be the 

 resting stages of other organisms. With regard to the literature on 



