74 p. T. CLEVE, SYNOPSIS OF THK NAVICULOm DIATOMS. 



I. Gracillimee. 



Artificial Jcey. 



. I Ends rounded ... .... ... . S. 



\ — capitate or rostrate . . . . 4. 



n j Stria not interrupted ... . . .P. sublinearia Gbun. 



\ — interrupted . . . . . .3. . 



„ f Strise almost parallel P. leptosoma Ghun. ') 



' \ — in the middle slightly radiate . . P. molaris Grun. 



. I Ends capitate . P. imdulata Geeg. 



\ — rostrate . . . . . . . P. gracillima Greg. 



1. P. gracillima Gkeg. (1856). — V. linear, triundulate, with rostrate to subcapitate ends. 

 L. 0,026 to 0,03; B. 0,005 mm. Areas indistinct. Striae, 18 to 22 in 0,oi mm. almost parallel. — 

 M. J. IV PI. I f. 31. Nav. gr. V. H. S. PL VI f. 24. N. mesotyla ScHUM. Tatra D. PL IV f. 51? 



Fresh water: Scotland (Greg.), Greenland ! 



2. P. undnlata Greg. (1854). — V. linear, with more or less distinctly triundulate margins 

 and broad, capitate ends. L. 0,03 to 0,035; B. 0,oog mm. Axial area indistinct; central area or-« 

 bicular or a transverse fascia. Strife 22 in 0,oi mm., almost parallel, convergent at the ends. — 

 M. J. II, PL IV f. 10. — Cl. D. of Finland p. 30 PL II f. 8. 



Fresh water: Sweden (Pautrask in Stensele Lappmark)! Finland, Savitaipale Dept! Scot- 

 land (Greg.). 



Var. subundulata Grun. — V. with less distinctly undulated margins. Striae 18 to 21 in 

 0,01 mm., not interrupted. — V. H. Types N:o 140. 



Fresh water: Scotland (V. H. T.). 



As far one may judge from the figures Nav. mesotyla Schum. and P. gracillima are the 

 same species, and the only difference between them and P. undulata consists in the broad, capitate 

 ends of the latter. 



3. P. snblinearis Grun. (1880). — V. narrow, linear, slightly gibbous in the middle, with 

 rounded ends. L. 0,02 to 0,03; B. 0,oo4 mm. Areas indistinct. Striae 21 to 24 in 0,oi mm. 

 slightly radiate in the middle, convergent at the ends. — Nav. subl. Grun. V. H. Syn. p. 76 

 PL VI f. 25, 26. P. tenuis Greg. M. J. 1854 p. 97 PL IV f. 9? 



Fresh water: Greenland! 



4. P. leptosoma Grun. (1880). — V. narrow, linear, with rounded ends. L. 0,o35 to 0,04; 

 B. 0,005 mm. Median line with approximate central pores. Axial area very narrow; central area 

 a broad, transverse fascia. Strite 14 or 17 (middle) to 16 or 20 in 0,oi mm. (at the ejids) almost 

 parallel. — Nav. leptos. Grun. in V. H. Syn. XII f. 29. 



Fresh water: Sweden (Rimforsa in Westergotland) ! Finland! 



5. P. molaris Grun. (1863). — V. linear, slender, with rounded or subcuneate ends. L. 

 0,033 to 0,05; B. 0,005 to 0,008 mm. Axial areal narrow or indistinct ; central area a broad, trans- 

 verse fascia, reaching to the margin. Striae 15 to 17 in 0,oi mm., slightly radiate in the middle, 

 convergent at the ends. — Nav. molaris Grun. Verb. 1863 p. 149 PL IV f. 26. V. H. Syn. 

 PL VI f. 19. Nav. macra A. S. Atl. XLIV f. 54. Nav. mesoleia Cl. N. R. D. p. 10 PL II f. 26. 



Fresh water: Norway (Dovre)! Scotland! Sweden! Denmark (Ringkebing Atl.), Finland! 

 Germany (Grun.), Brazil! Demerara River! Cape Horn! Bengal! 



P. molaris is nearly akin to P. leptosoma, which differs by nothing except the less radiate 

 median and the closer terminal striae. 



') Conf. P. isostauron Grun. 



