{ 



KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 11 



Valve with undulate margins N. Sancti Thomce Cl. 



M; 



6- > 



— non — — 7. 



Fresli water habitat N. ludloviana A. S. 



Marine 8. 



„ ) Strise not reaching to tlie margin N. subalata Gkun. 



\ — reaching 9. 



„ j Ends obtuse 10. 



\ — acute 14. 



.. I Ends broad, rounded 11. 



\ — not very broad 13. 



..^ ( Axial area gradually dilated to the middle N. jamalinensis Cl. 



I — — abruptly — — a central area N. opima Geun. 



Size small. L. about 0,06 mm 13. 



— large. L. about 0,1 mm N. distans W. Sm. 



^ ., i' Axial area lanceolate N. Nicmensis Pee. 



16. |^*^« 



. ., ( Axial area 



\ — — abrnptly dilated into an orbioular central area JV. salva A. S. 



... ( Striae radiate throughout N. Platessa Cl. 



\ — transverse in the ends 15. 



.j, ( Stri» crossed by a blank band N. Bruchii Grun. 



\ — not — — — N. Ämicorum Geun. 



Strise radiate 17. 



parallel 82. 



.._ J Terminal striae parallel or convergent 18. 



I — — radiate 54. 



.r, J Terminal striae crossed by a lunate band : N. annulata Geun. 



t — -not — - — 19. 



..Q I Terminal striae genuflexed N. ohlonga Kutz. 



t — — not — 20. 



£,„ I Stri» crossed by lateral areas or by narrow blank bands 30. 



^''^ i - not - - - - - - 21. 



Q.| ( Median striae of unequal length 22. 



\ — — equal — 36. 



g„ ( Valve lanceolate, rostrate-capitate 28. 



^^- \ - - not - - 23. 



„„ ( Valve acnte 24. 



obtuse 25. 



g , J Median striae alternately longer and shorter N. Salinarum v. intermedia. 



"* ' I — — shorter than the others N. notabilis Pant. 



„, I Striae iine, 20 in 0,oi mm N. bottnica Geun. 



\ — coarse, 8 to 9 mm 26. 



»„ j Striae coarsely lineate 27. 



1 — finely — N. digito-radiata Gkeg. 



„- I Striae 6 in 0,0 1 mm N. peregrina Ehb. 



' \ — 9 — — N. Eeinhardtii Geun. 



„„ j Terminal striae strongly convergent N. Wilczekii Geun. 



t — — parallel 29. 



15 to 

 .5 m 

 j Striae crossi 



i" ~ 



1 — lanceolate N. Haueri Geun. 



„„ j Lateral area unilateral N. Anthracis Be. a. Cl. 



\ — areas bilateral N. Bruchii Geun. 



„ . ) Longitudinal bands two on each side 35. 



■ I — — several — iV. TitsmlaBsB. 



g. J Length 0,025 to 0,037 mm N. Salinarum Geun. 



1 — 0,115 mm N. Eho Cl. 



„„ j Striae crossed by a lateral area 31. 



— two or more blank bands 34. 



„.. j Valve obtuse 32. 



\ — acute 33. 



„„ ( Valve linear, with rounded ends N. obtusa Cl. 



' Conf. N. basaltce proxima Be. and N. aquitanice Be. (additional). 



