K0N6L. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. X:(1 3. 



p. f Pnncta forming longitudinal rows parallel to the margins of the valve . . N. Theta Cl. 

 ' \ — not — — — — — — — N. sciitiformis Gbun. 



StrisB very fine, about 30 in 0,oi mm. . . .... N. Pusio Cl. 



coarser, about 17 in 0,0 1 mm. . . . . N. surinamensis Cl. 



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1. N. Theta Cl. (1893). — V. elliptical. L. 0,0.55; B. 0,o28 mm. Axial area narrow, 

 linear; central area small, orbicular. Strise radiate (in the ends nearly parallel) in the middle, 

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

 stinctly punctate; puncta 21 in 0,oi mm. forming longitudinal rows parallel with the margin. — 

 Diatomiste II p. 56 PI. Ill f. 5. 



Fresh water: Oregon, fossil. 



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

 ram. Axial area narrow, linear. Central area moderately large, orbicular. Strise about 2.t in 

 0,01 mm., gently curved and radiate at the ends, iinely but distinctly punctate. Median strise 

 more coarsely punctate than the others. — Diatomiste II p. 14 PI. 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,oi mm. radiate at 

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



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



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

 mm. Strise 27 in 0,oi 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. Strise 25 to 29 in 0,oi mm., radiate at the ends, in the middle of 

 unequal length, finely punctate. '— M. J. IV, I. f. 22. Grun. Verb. 1860 p. 550 PL IV f. 9. 

 Done. B. D. p. 22 PL HI f. 11. Lagst. 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 Abo), Sweden! Scotland! France (Vosges)! Oregon, foss. ! 



5. N. scutiformis Grun. (1881). — V. elliptical, 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, orbicular. Strise 18 to 20 in 0,oi 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! Umea, Sweden, fossil! 



6. N. Tau Cl. (1893). — V. elongated, slightly biconstricted, with cuneate ends. L. 0,037; 

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

 mm. radiate at the ends; in the middle of unequal 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. 0,013 mm. Median line with the terminal fis,sures in contrary direction. Axial area indistinct 

 or very narrow. Central area small. Strise 17 in 0,oi mm., in the middle alternately longer and 

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



Fresh water: Surinam! 



Kongl. Sv. Vet. Akad. Hand). Band 27. N:o 3. 



