KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 27. N:0 3. 13 



Valve rostrate ti5. 



64 



non 



66. I 



{ 

 { 



StrisB coarsely lineate 67. 



— finely — 68, 



„^ i' Median strise alternately longer and sliorter 66. 



^^- ^ - not - - - - 69. 



„_ j Central area with stigmas iV. dementis Geun. 



„„ I Strise about 9 in 0,oi mm N. Gastrum Ehb. 



' \ — — 17 — — N. platystoma Ehb. 



„„ f Valve linear N- falaisiensis Gbun. 



I — lanceolate to elliptical 70. 



„„ j Valve very convex N. crucifera Gkun. 



\ - not - 71. 



„., j Strise coarsely lineolate N. Placentula Ehb. 



1 — finely — 72. 



„„ I Central area small S. anglica Ralfs. 



' \ — — large iV. dicephala W. Sm. 



„„ I Median strise alternately longer and shorter 76. 



'"^- 1 - - not - - - - 74. 



„. J Size small. L. 0,03 mm N. arenariceformis Pant. 



larger. L. 0,OG to 0,1 mm 75. 



. f Size 



M - 



„. / 3,5 to 4 times longer than broad JV. valida Cl. a. Geun. 



■ t 5 to 6 — — — — N. Hasta Pant. 



Central area small or indistinct 77. 



medium sized or large 80. 



„_ j Ends conical N. inflexa Geeg. 



-I' 



f Endi 



not — 78. 



_„ j Strise sliglitly radiate N. arenicola Geun. 



\ — strongly — 79. 



_j. I Fresb water habitat N. lanceolata Kutz. 



\ Marine N. solaris Geeg. 



y_ J Strise coarse 5 to 6 in 0,0) mm 81. 



flner 10 in 0,oi mm 'N. oviformis Cl. 



coarsely lineate JV. pennata A. S. 



finely — N. consanguinea Cl. 



( Stri; 



81. {^'^ 



„„ J Size small, L. less tlian 0,03 mm 83. 



\ — larger. L. more — 86. 



„„ j Strise 15 in 0,01 mm 84 



I StrisE 



t — 22 to 23 mm 85. 



J Lineolse forming longitudiiial strise N. mollis "W. Sm. 



\ — not — — — N. incerta Gecn. 



Frnstnles in gelatinons tubes N. corymbosa Ag. 



— the interiör of algse N. nidulans Cl. 



Frnstule arcuate JV. sibirica Geun. 



not — 87. 



o- j Strise crossed by lateral areas or blank bands 97. 



{ 



85.]^ 



86. I^-^^^* 



( Stria 



I • — not — — — — — 88. 



Strise coarsely lineate JV. Satura A. S. 



— finely — 89. 



„q j Lineolse forming oblique or longitudinal fine strise 103. 



"^- t - not 90. 



cin J V^l'^6 very convex 91. 



-*"• t - not - ■ 93. 



„., ) Valve asymmetrical N. Scoliopleura A. S. 



i — symmetrical 92. 



„„ i Frnstule arcuate N. Cubitus Be. a. Temp 



\ — not — JV. Northumbrica Donk. 



.„ f Valve linear JV. jejtina A. S. 



\ — lanceolate or rhomboidal 94. 



