Naviculse Minusculse Cl. 



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

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



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



Artificial key. 



^ j Marine species 3. 



I Fresh-water species 3. 



j Valve elliptical N. debilissima Geun. 



\ — lanceolate .... • N. bahwsiensis Gbun. 



( Striae coarse (17 in 0,oi mm.) N. lucidula Geun. 



\ — flne (30 and more in 0,0 1 mm.) 4. 



I Valve elliptical 5. 



\ — lanceolate 8. 



j, I StriEB indistinct • N. pelliculosa Bréb. 



[ 



— abont 30 in 0,01 mm 6. 



( Strise radiate N. atomus Naegeli. 



\ — parallel 7. 



) Valve broadly elliptical N. muralis Gkuit. 



\ — narrow N. exilissima Geun. 



Valve broadly lanceolate N. minusmla GKnn. 



narrow — N. microcephala Geun. 



{ 



1. N. pelliculosa (Beéb.) Hilse (18(52). — V. very slightly silicious, elliptical, with broad 

 and rounded ends. L. 0, 009; B. 0,oo4 to 0, 005 mm. Strise extremely fine. — Frustulia pellic. 

 Bréb. (accoi-ding to G-runow). Frustulia sp. Geun. Verh. 1860 p. 573 Pl. VII f. 18. Nav. pell. 

 HiLSB Eabh. a. E. N:o 1-265. V. H. Syn. Pl. XIV f. 32. 



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



2. N. debilissima Geun. (1884), — V. elliptic-lanceolate L. 0,007; B. 0,oo5 mm. Stria? 

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



Marine: Franz Josefs Land. 



3. N. muralis Geun. (1880). — V. elliptical, with ronnded ends. L. 0,oo6 to 0,012; B. 0,oo4 

 mm. Areas indistinct. Strise very slightly radiate, about 30 in 0, 01 mm. — V. H. Syn. Pl. XIV 

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



Fresh water. 



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

 Areas indistinct. Striee abotit 40 in O.oi mm., almost parallel; the median more distant. — V. H. 

 Syn. p. 108 Pl. XIV f. 30. 



Fresh water: Beigium (V. H.). 



