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



8. N. dnbiuin Ehb. (1843). — V. elliptical, sometimes slightly biconstricted, with obtuse, 

 subrostrate, or almost apiculate ends. L. 0,o3 to 0,o37.'i; B. 0,oi mm. Striae 20 to 24 in 0,oi mm. 

 — Nav. dubia Ehb. Am. p. 130 PI. II f. 2, 8. KtJTZ. Bac. p. 96 PL XXVIII f. 61. Greg. M. J. 

 1856, IV PI. I f. 3. ScHUM. P. D. 1 Nacht. p. 21 f. 25. A. S. Atl. XLIX £ 7, 8, 24 to 26. 

 Nav. Peisonis Grun. Verh. 1860 p. 544 PI. Ill f. 28. Nav. Iridis var. dubia V. H. Syn. p. 104 

 Suppl. B. f. 32. Nav. incurva var. niinuta Gutwinsky Materyjaly p. 22 PL I f. 18. 



Fresh, sometimes brackish water: Sweden ("Wester botten to Skane)! Gulf of Bothnia! Scot- 

 land (Greg.). Neusiedler See, Hungary (Grun.). Bengal! Australia (Blue Mountains)! New Zea- 

 land! North America (Port Hope, Ducks Pond, Lost Spring Ranch Cal.)! Surinam! Ecuador! Puerto 

 Monte, Chile! Argentina! 



9. N. dilatatum Ehb. (1843). — V. broadly elliptical, with subrostrate ends. L. 0,06; 

 B. 0,025 mm. Strise 16, puncta 17 in 0,oi mm. — Nav. dilatata Ehb. Am. p. 130. A. S. Atl. 

 XLIX f. 6. 



Fresh water: Finland (Vasa! Pudasjarvi Atl.). 



10. N. citreum A. S. (1877). — V. broadly lanceolate. L. 0,o7 to 0,io; B. 0,o4 to 0,o.55 mm. 

 Striae 16 to 17, puncta 17 to 19 in 0,oi mm. — Nav. citrea A. S. Atl. XLIX f 12. 



Fresh water: Demerara River! 



11. N. tumescens Grun. (1877). — V. broadly lanceolate. L. 0,i6; B. 0,o6 mm. Striae 16. 

 puncta 17 in 0,oi mm. — Nav. fir ma var. tumescens Grun. A. S. Atl. XLIX f. 10. 



Fresh water: North America (Bemis Lake! Cherry field! Monmouth! Troy!). 



Additional. 



To Neidium perhaps belongs Navicula includens Pant. Ill (PL XIII f. 201), unknown tc 

 the author. 



Pseudoampliiprora Cl. (1881). 



Valve more or less lanceolate and convex. Median line straight. Central nodule transversely 

 dilated into a stauros, not reaching the margin, but abutting on two longitudinal lines, one on each 

 side of the median line. Axial area indistinct, central area a transverse fascia. Striae nearly 

 parallel, composed of fine puncta. Connecting zone not complex. — The cell-contents of P. stauro- 

 ptera have two chromatophore-plates along the valves. They have entire margins and a deep, 

 narrow sinus from the apices, below the median line. Their substance is thinner below the longi- 

 tudinal lines. 



In the year 1881 (New and rare D. p. 13) I proposed to include in a section Pseudo-amphi- 

 prora of Navicula a few forms, among which was Amphora staitroptera Bail., synonymous with 

 Amphiprora lepidoptera Greg. (D. of Cl. PI. XII f. 59 c) and A. ohtusa Greg. (1. c. f. 60). This 

 small group is very interesting and merits to be regarded as a separate genus, the systematic place 

 of which is between Naviculce Lyratce and Caloneis. 



All the species are marine and inhabit both arctic and tropical seas. 



Artificial key of species. 



Stauros narrow . . ... P. impleta Cl. a. Gkov. 



— broad .... . . .2. 



V. with cuneate ends p. polygona Brun. 



v. lanceolate . . . . 3. 



