68 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Artificial key. 



1 



I Valve elongated, 3 to 6 times longer than broad . • ... 3. 



\ — broad, 2 to 3 ... . ■ 7. 



Margins parallel .... ... ■ • . . . 3. 



2. -J — convex . . . 4. 



— undulating . . . 5. 



Ends rounded . N. bisulcatum Lagst. 



— cuneate . . N. amphigomphus Ehb. 



— rostrate . . N. affine Ehb. 

 Ends rounded ... N. Iridis Ehb. 



— subrostrate . . N. Iridis var. 



— rostrate-capitate 

 Ends broad, rounded . . . 



1 — cuneate 



6. 



Strise slightly oblique 

 — strongly 



N. productum W. Sm. 



. N. affine var. 



6. 



. N. Hitchcockii Ehb. 



N. oblique-striatum A. S. 



L. 0,03 to 0,0 4 mm. ... ■ N. dubium Ehb. 



L. 0,0 6 mm . ... . N.'dilatatum Ehb. 



^ L. 0,01 to 0,1 mm. . . . N. citreum A. S. 



II. 0,16 mm. . . . . . . N. tumescens Gkun. 



1. N. bisulcatum Lagst. (1873). — V. linear, with roimded ends. L. 0,04 to 0,o7; B. 0,oo8 

 to 0,00 9 mm. Strise 28 to 30 in 0,ai mm., distinctly piinctate. — Navic. bisulcata Lagst. Spitsb. 

 D. p. 31 PL I f. 8. A. S. Atl. XLIX f. 15, 17. N. scita W. Sm. Ami. Mag. n. hist. XIX p. 10, 

 PL II f. 4 (1857)? 



Fresh water (alpine regions): (ireenland! Spitsbergen! Beeren Eiland (Lagst.)! Dovre, Nor- 

 way! Sweden (Areskntan, Westerbotten etc.)! Finland! Lac Gerardmer (Vosges)! Argentina! 



2. N. affine Ehb. (1843). — V. linear, with rostrate ends. 



Var. longiceps Greg. (1856). — V. small, frequently with undulating margins. Ends broad, 

 rostrate or rostrate-capitate. L. 0,03; B. 0,oo5 mm. Strise very fine. — Nav. longiceps Gbbg. M. 

 J. IV PL I f. 27. 



Fresh water: Greenland! Scotland (Greg.)! 



Var. undulata Geun. (1860). — V. slightly triundulate, with broad, rounded ends. L. 0,0 7; 

 B. 0,013 mm. Strise 24 in 0,oi mm. — Nav. aff. var. undulata Grun. Verb. 1860 p. 544. PL V 

 f. 6. V. H. Syn. PL XIII f. 6. 



Fresh water: Sweden (CL M. D. N:o 103), Belgium (V. H.). 



Var. amphirhynchus Ehb. (1843). — V. with protracted, rostrate-capitate ends. 



Forma minor: L. 0,04 to 0,o5; B. 0,oo8 to 0,013 mm. Striae 25 to 27 in 0,oi mm. 



Fresh water: Sweden (Upsala)! Astralia (Blue Mountains)! 



Forma major: L. 0,09; B. 0,oi mm. Striae about 16 in 0,oi mm. — Nav. a//?ms Ehb. Am. 

 Ill: 1, f. 10 etc. Nav. amphirhynchus W. Sm. B. D. XVI f. 142. Donk. B. D. p. 34 PL V f. 9. 

 A. S. Atl. XLIX f. 27 to 30. Nav. aff. var. amphirh. Grun. Verb. 1860 PL Vf. 5, 11. Nav. Iridis 

 var. amphirh. V. H. Syn. PL XIII f. 5. 



Fresh water: Spitsbergen (Lagst.), Beeren Eiland (Lagst.), Scotland! England! Belgium 

 (V. H.)! Sweden! Finland! New Zealand! 



Var. genuina Cl. — V. with rostrate, less protracted ends. 



Forma minor: L. 0,045 to 0,o65; B. 0,oo8 to 0,oi3 mm. Strise 22 to 29 in 0,ni mm. 



Nav. affinis Ehb. Am. II: 2. f. 7; 4 f. 4. KuTz. Bac. XXVIII f. 65. Nav. af finis var. A. S. Atl. 

 XLIX fig. 20 to 23. Nav. bisulcata var. turgidula Lagst. Spitsb. D. p. 32 PL I f. 9. 



Fresh water: Spitsbergen (Lagst.), Lappland! Finland (Tulomian Lappmark)! Italy (Atl.)! 

 Australia (Blue Mountains and Tasmania)! 



