KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 



27. n:o 3. 183 



This subgenus comprises forms, which appear not to be very closely connected. A. hyper- 

 borea seems to be akin to the linear forms of Microneis. A. gibberula and A. Holstii are probably 

 allied to the section Mesolei^ of Navicula and ought perhaps to be placed by the side of C. mi- 

 nuta. To C. quarnerensis and the others I am unable to find any allied forms among the Navicula. 



Artificial key. 



{Valve linear A. hyperborea Gkdk. 

 — lanceolate or rhomboidal .... 2. 



— ■ elliptical . ... . .5. 



„ J Area of the upper valve granulate A. Lilljebergii Gbun. 



"^^ \ - - - -not - 3. 



'J I TTpper valve with an horseshoe-like mark A. Yaszaryi Pant. 



' \ — — without — — — 4. 



Striae of the upper valve 23 in 0,oi mm ... A. gibberula Gkun. 



— _ 14 _ _ A. Holstii Cl. 



L. about 0,01 mm 6. 



L. 0,02 mm. or more 7- 



StriiB of the upper valve unilaterally interrupted A. americana Cl. 



— — — — .- not — — C. pygmoea Schum. 



Upper valve with an horseshoe-like mark A. Lagerheimii Cl. 



5. p- ^^ 



( L. 0,02 mm. or more 7. 



6 i 

 ■ ( — — — — .- not — — C. pygmoea Schum 



7. I 



I — — without — — — S. 



J Striae of the upper valve 9 in 0,01 mm C. quarnerensis Getjn. 



\ — — — — 11 to 12 in 0,01 mm 9. 



Area of the upper valve dilated in the middle . ... . . . C. biharcnsis Pant. 



_ _ _ not — — — C. Pelta A. S. 



»■( 



1. A. Yaszaryi Pant. (1893). — Outline rhomboid, subacute. L. 0,o6; B. 0,o3 mm. Upper 

 V. unknown. Lower V. with narrow axial area and transverse, outwardly fimbriate central area. 

 Median strite transverse and of unequal length, 13 in 0,oi mm. Other stria; strongly radiate 

 throughout, about 20 in 0,oi mm., punctate. — Nav. Vasgaryi Pant. Ill PI. XVI f. 239. 



Habitat? Nyermegy (Pant.). 



Var. oregonica Cl. (1893). — Outline lanceolate with subrostrate, obtuse ends. L. 0,03; 

 B. 0,013 mm. Upper V. with lanceolate axial area, a third as broad as the valve, and with a 

 unilateral horseshoe-shaped marking. Costte slightly radiate, about 16 in 0,oi mm. alternating 

 with fine obliquely arranged puncta, about 30 in 0,oi mm. Lower valve without axial area and 

 with a large central area, fimbriate outwards. Median strife of unequal length and transverse, 

 about 18 in 0,oi mm. Strise of the other portions of the valve very radiate, becoming closer 

 towards the ends, about 26 in 0,oi mm. — Diatomiste II p. 57 PL III f. 15, 16. 



Fresh water: Oregon, fossil! 



This is a very interesting species, the lower valve of which perfectly resembles that of 

 Actinoneis. It appears to be akin to A. heteromorpha of the subgenus Actinoneis. There can be 

 no doubt that Nav. Vassaryi Pant., which represents the lower valve, is very nearly related to 

 the form from Oregon, of which I have examined an entire frustule. The differences are slight, 

 as to the size, the outline, and the coarseness of the striation, for which reason I am not inclined 

 to consider them as distinct species. 



2. A. hyperborea Grun. (1882). — Outline linear, with broad, sometimes cuneate, ends, 

 slightly constricted in the middle. L. 0,o26 to 0,o-28; B. 0,oo65 to 0,oo8 mm. slightly arcuate. 

 Upper V. with obsolete median line and broad, linear area. StriiB 27 in 0,oi mm., radiate at the 

 ends. Lower V. without areas. Median striiB 24, terminal 30 in 0,oi mm. — Cl. M. D. N:o 314. 

 Franz Josefs Land D. p. 102 PI. I f. 4, 5. 



Marine: Franz Josefs Land (Grun.). 



