Naviculse Minusculse Cl. 



Valve small, broadly lanceolate to elliptical, slightly silicions. Areas indistinct. Structure 

 slightly radiate, very fine or indistinct striae. Connecting zone not complex. 



The species of this group are usually of extremely small size, and live in fresh or salt water. 



Artificial key. 



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^ , Marine species 2. 



Fresh-water species 3. 



Valve elliptical N. debilissima Gbun. 



— lanceolate .... • N. bahu.siensis Geun. 



., , Striae coarse (17 in (),ni mm.) N. lucidula Grun. 



o. 



M 

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. . Valve elliptical 5. 



lanceolate 8. 



fine (HO and more in 0,oi mm. 



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J, j Stria indistinct N. pelliculosa Breb. 



I — about 30 in 0,oi mm 6. 



„ I Striae radiate N. atomus Naegeli. 



\ — parallel 7. 



j Valve broadly elliptical N. muralis Grun. 



\ — narrow N. exilissima Grun. 



Q J Valve broadly lanceolate N. minuscnla Grun. 



narrow — N. microcephala Grun. 



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1. N. pelliculosa (Br6b.) Hilse (18»i2). — V. very slightly silicious, elliptical, with broad 

 and rounded ends. L. 0,oo9; B. 0,oo4 to 0,oo5 mm. Striae extremely fine. — Friistulia pellic. 

 Br6b. (according to Grunow). Frustulia sp. Grun. Verb. 1860 p. 573 PI. VII f. 18. Nav. pell. 

 HiLSE Rabh. a. E. N:o 1265. V. H. Syn. PI. XIV f. 32. 



Fresh water: Germany (A. E.), France (Breb.). 



2. N. debilissima Grun. (1884), — V. elliptic-lanceolate L. O.oor; B. O.oo.i mm. Strise 

 not seen. — Franz Jos. Land D. p. 104 (52) PI. I f. 42. 



Marine: Franz Josefs Land. 



3. N. muralis Grun. (1880). — V. elliptical, with rounded ends. L. 0,006 to 0,012; B. 0,oo4 

 mm. Areas indistinct. Striae very slightly radiate, about 30 in 0,oi mm. — V. H. Syn. PI. XIV 

 f. 26 to 28. N. Atomus Schum. P. I). I Nachtr. p. 21 f. 24? 



Fresh water. 



4. N. exilissima Grun. (1880). — V. linear-elliptical. L. 0,oo5 to 0,oi; B. 0,oo3 mm. 

 Areas indistinct. Striae about 40 in O.oi mm., almost parallel; the median more distant. — V. R. 

 Syn. p. 108 PI. XIV f. 30. 



Fresh water: Belgium (V. H.). 



