{ 



,.r f Median stri; 

 fa!), i 



KOXOL. SV. VKT. AKADEMIKNS II AM)I,IN(;A1{. HAND 27. .\:o 3. 



„ , I Valve rostrate (i5. 



non — (.-J. 



striae alternately longer and shorter 66. 



not — — — — 69. 



,,.. ( Stria) coarsely lineate 07. 



\ — finely - 68. 



^_ I Central area with stigmas N. Clcnientis Grun. 



I — — without — iV. leptostigma Eub. 



, ) StriiB about 9 in 0,oi mm N. Gastrnni Eub. 



' \ — — 17 — — N. platystoma Enn. 



I Valve linear N. falaisiensis Grun. 



" ' \ — lanceolate to ellijitical 70. 



„ j Valve very convex N. crucifera Grun. 



1 - not - 71. 



„., ) Striae coarsely lineolate N. Placcntula Ehb. 



"i — finely — 72. 



_,^ j Central area small N. anglica Ralps. 



* ( — — large N. dicephnln W. Sm. 



_„ j Median stria alternately longer and shorter 76. 



' \ — — not — — — — 



74 



I — larger. L. 0,06 to 0,i mm 75 



75 



Central area small or indistinct 77. 



medium sized or large 80. 



__ I Ends conical N. inflexa Greg. 



\ - not - 78. 



„ I Striae slightly radiate N. arenicola Grun. 



\ — strongly — 79. 



_ ( Fresh water habitat N- lanceolata KtJTZ. 



Marine N- Solaris Greg. 



_. I Size small. L. 0,02 mm N. arenarimformis Pant. 



( 2,5 to 4 times longer than broad N. valida Cl. a. Grun. 



■ 1 5 to 6 — — — — N. Hasta Pant. 



Striae coarse 5 to 6 in U,(ti mm 81. 



finer 10 in 0,oi mm N. oviformis Cl. 



80. 1^*^' 



„.. i Striae coarsely lineate N. pennata A. S. 



finely — N- consangiiinea Cl. 



imall, L. less than 0,03 mm 83. 



arger. L. more — 86. 



Striae 15 in 0,0 1 mm 84. 



I — 22 to 23 mm 85. 



, ( Lineolae forming longitudinal striae N. mollis W. Sm. 



85. i 



\ — not — — — iV. incerta Grun. 



Frustules in gelatinous tubes N. corymbosa Ag. 



— — the interior of algae N. nidulans Cl. 



Frustule arcuate N. sibirica Grun. 



^^1 - not - 87. 



„_ j Striae crossed by lateral areas or blank bands 97. 



«7- -j _ not - - - - - 88. 



J Striae coarsely lineate N. Satiira A. S. 



«»• \ _ finely - 89. 



„„ } Lineolae forming oblique or longitudinal fine striae 103. 



^^- \ - not 90. 



r,^ ( Valve very convex 91. 



''^- { - not - 93. 



. I Valve asymmetrical N. Scoliopleura A. S. 



"I — symmetrical '2- 



( Frustule arcuate N. Cubitus Br. a. Temp 



I _ not — N'. Northumbrica Donk. 



( Valve linear N. jejuna A. S. 



\ — lanceolate or rhomboidal 94. 



