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



j Median o1)lique striae more distant tlian tlie others 17- 



^^- \ - - - not 18- 



Valve linear-lanceolate P- atistrale Geck. 



' lanceolate P- Normcinii Ralf. 



f Transverse and oblique striai equldistant 19- 



18. •! — strise closer than tlie oblique 21. 



{ — — more distant — 24. 



I Valve narrow P- delicatulum W. Sm. 



^^- \ - broad 20. 



J Stria) 28 in 0,01 mm P- javanicum Grcn. 



■^^- ^ 18 to 22 — P migxilatum Quek. 



J Oblique striee at an angie of 90" 22. 



"^ j — — — about 60° P elongatum "W. Sm. 



J Ends with a lunate mark P kergiielense Grun. 



/VÄ. < - ^*> 



\ — withont — 23. 



Median line central at tlie ends P longum 



_ _ excentric P subrigidum Gi 



Ends obtuse 25. 



" ' \ — acute 28. 



„,. j Valve large, about 0,3 mm. in length 26. 



■^ ' \ — small — 0,1 — or less 27. 



i Valve straiglit P rigidum W. Sm. 



\ — sigmoid P prcelonguni Cl. 



g, (Transverse striae 24 in 0,0 1 mm P salinarum Geun. 



"i — 27 — P. minutum Grun. 



( Valve linear, strongly sigmoid at tlie ends P Brunii Cl. 



" ■ ( — lanceolate — — — 29. 



I Transverse striae 17 in 0,0 1 mm P Griindleri Gettn. 



■^^- \ — — 21 to 24 — P Stuxbergii Cl. a. Gr. 



i Median line flexuose P incertum Pek. (P falcafum Donk). 



3^- \ - - not 31. 



I Median line enclosed between longitudinal lines P Exnl Cl. 



^^- i - - not - - - 32. 



j Central area large P mnbilicahim Cl. 



'^' \ — small or indistinct • "33. 



(,„ jOblique striae at an angle of 90° 34. 



•''^- \ - _ _ _ less than 90° 37. 



.Valve broad, lanceolate 35. 



34 ' 



{ 



— narrow, linear-lanceolate 36. 



.-.^ J Median oblique striae more obtuse than the others P maju,s Grdn. 



■^"^- \ — — — not — — P Hcros Cl. 



.. . j Frustnle arcnate P Weissflogii Gkun. (P. fonnosum var. Arais). 



'^''- \ — not P formostim W. Sm. 



„_ ( Valve linear 38. 



' ' \ — lanceolate 40. 



.,„ ( Valve carinated P cnrinatum Donk. 



^^- \ - not 39. 



( Median line strongly excentric P obsmrum "W. Sm. 



■ \ — — excentric in the ends P speciosum W. Sm. 



,„ f Ends subrostrate P ^Estuarii Bréb. 



*0- i _ not 41. 



.^ ( Valve rhomboidal 42. 



\ — narrow lanceolate 43. 



) Transverse striae about 17 in 0,0 1 mm P. rhombcum Grun. 



^ \ — — — 24 — P latum Cl. 



,., [Striae about 22 in O.oi mm P aciitum Norm. 



20 — P maroccanum Cl. 



I Stri» al 



1. P. Nubeculii "W. Sm. (1853). — V. narrow lanceolate, not, or slightly, sigmoid, with snb- 

 cute ends, L. 0,09. «> to 0,i6; B. O,oifi to 0,02 uam. Median line straight, central. Transverse and 



