KONGL. SV. VET. AKADEMIENS HANDLIN GAIi. BAND 27. N:() 3. 9 



j. ( Puncta forming longitudiual rows parallel to the margins of tlie valve . . . N. Tlieta Cl. 



\ — not — — — — — — — N. scutiformis Geun. 



„ I Strise very fine, about 30 in 0,oi mm N. Pusio Cl. 



\ — coarser, about 17 in 0,01 mm N. surinamensis Cl. 



1. N. Theta Cl. (1893). — V. elliptical. L. 0,0.55; B. 0,028 mm. Axial area narrow, 

 linear; central area small, orbicular. Strite racliate (in the ends nearly parallel) in tlie middle, 

 where they are alternately longer and shorter, 20 in 0, 01 mm. at the ends 25 in 0, 01 mm., di- 

 stinctly punctate; puncta 21 in O, di mm. forming longitudinal rows parallel with tlie margin. — 

 Diatomiste II p. 5C Pl. III. f. 5. 



Fresh water: Oregon, fossil. 



2. N. limicolii Cl. (1893). — V. elliptical, with rounded, ohtuse ends. L. 0,04 6; B. 0,oi7 

 mm. Axial area narrow, linear. Central area moderately large, orbicular. Striee about 25 in 

 0,01 mm., gently curved and radiate at the ends, finely biit distinctly punctate. Median striaä 

 more coarsely punctate than the others. — Diatomiste II p. 14 Pl. I f. 12. 



Mouth of rivers: Cameroon, Africa (leg. Dusen). 



3. N. Pusio Cl. N. Sp. — V. elliptical, with broad rostrate ends. L. 0,oi6; B. 0, 007 mm. 

 Axial area very narrow. Central area small. Strise very fine, about 30 in 0, 01 mm. radiate at 

 the ends, in the middle alternately longer and shorter, closer towards the ends. — Pl. II f. 3. 



Fresh water: Rötorna Lake, N. Zealand (leg. Berggren). 



N. arcuata Pant. III Pl. VI f. 97 represents a similar, but larger form. L. 0, 03; B. 0,oi6 

 mm. Strise 27 in 0, 01 mm. 



4. N. cocconeiformis Greg. (1856). — V. elliptical to rhomboidal, obtuse. L. 0,02 6 to 

 0,032; B. 0,009 to 0,013 mm. Central pores of the median line distant. Axial area indistinct; 

 central area small, elongated. Strite 25 to 29 in 0, 01 mm., radiate at the ends, in the middle of 

 unequal length, finely punctate. — M. J. IV, I. f. 22. Grun. Verh. 1860 p. 550 Pl. IV f. 9. 

 DoNK. B. D. p. 22 PL ni f. 11. Lägst. Spitsb. D. p. 32 Pl. II f. 8. V. H. Syn. Pl. XIV f. 1. 



Fresh water, especially in arctic or alpine regions: Spitsbergen! Norway, Dovre! Finland 

 (Russian Lappland to Åbo), Sweden! Scotland! France (Vosges)! Oregon, foss.! 



5. N. scutiformis Grun. (1881). — V. elliirtical, with broad, rounded ends. L. 0,04; B. 0,024 

 mm. Central pores of the median line distant. Axial area very narrow, linear; central area 

 large, orhicular. Striaj 18 to 20 in 0, 01 mm. (in the middle, closer towards the ends), strongly 

 radiate; the median of unequal length, not more coarsely punctate than the others. — A. S. Atl. 

 LXX f. 62. 



Fresh water: Stavanger, Norway (A. S. Atl.), Lule Lappmark! Umeå, Sweden, fossil! 



6. N. Tan Cl. (1893). — V. elongated, slightly biconstricted, with cuneate ends. L. 0,03?; 

 B. 0,01 mm. Axial area very narrow; central area of medium size, rounded. Strise 20 in 0, 01 

 mm. radiate at the ends; in the middle of uneqnal length. — Diatomiste II p. 14 Pl. I f. 11. 



Fresh water: Demerara River! 



7. N. surinamensis Cl. N. Sp. — V. elliptic-lanceolate with rostrate, broad ends. L. 0,027; 

 B. 0,0 13 mm. Median line with the terminal fissnres in contrary direction. Axial area indistinct 

 or very narrow. Central area small. Strite 17 in O.oi mm., in the middle alternatelj' longer and 

 shorter, radiate at the ends. — Pl. II f. 1. 



Fresh water: Surinam! 



Kongl. Sv. Vet. Akad. Handl. Band 27. N:o 3. 



