74 P. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



I. GraeiUimse. 



Arfificial 'kcy. 



Ends rounded S. 



— capitate or rostrate 4. 



Striae not interrupted P. stoblinearis Geun. 



— interrupted 3. 



M 



„ / Stri» almost parallel P. leptosoma Grdn. ') 



. j Ends capitate P rmdidata Greg. 



— in tlie middle sliglitlj' radiate P. mälaris Grun. 



I 



rostrate P. gracillima Greg. 



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

 L. 0,026 to 0,03; B. 0,00.^ mm. Areas indistinct. Strise, 18 to 22 in 0,oi mm. almost parallel. — 

 M. J. IV Pl. 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. undulata Greg. (1854). — V. linear, with more or less distinctly triundulate margins 

 and broad, capitate ends. L. 0, 03 to 0,03.5; B. 0,ooc mm. Axial area indistinct; central area or- 

 bicular or a transverse fascia. Strite 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 (Pauträsk in Stensele Lappmark)! Finland, Savitaipale Dept! Scot- 

 land (Greg.). 



Var. subundulata Grun. — V. with less distinctly undulated margins. Strise 18 to 21 iai 

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



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



As far one may judge from the fignres Nnv. mesotyla Schom. and P. gracilUma are the 

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

 ends of the latter. 



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

 rounded ends. L. 0, 02 to 0, 03; B. 0,oo-i mm. Areas indi.stinet. Striee 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. O.dof) mm. Median line with approximate central pores. Axial area very narrow; centi^al area 

 a broad, transverse fascia. Strite 14 or 17 (middle) to 16 or 20 in 0, 01 mm. (at the ends) almost 

 parallel. — Nar. Icptos. Grun. in V. H. Syn. XII f. 29. 



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



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

 0,033 to 0,0.5; B. 0,00!) to 0,008 mm. Axial areal narrow or indistinct; central area a broad, trans- 

 verse fascia, reacliing to tlie margin. Stria^. 15 to 17 in 0,oi mm., slightly radiate in the middle, 

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

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



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

 (TPriiiany (Grun.), Brazil! Demei'ara River! Cape Horn! Bengal! 



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

 median and the closer terminal strise. 



') Conf. P. iaostauron Grun. 



