78 



1'. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



K. 

 17. 

 18. 

 19. 

 20. 

 21. 

 92. 

 23. 



24. 



2(j. 

 27. 

 28. 

 29. 

 ;iO. 

 31. 

 32. 

 33. 

 34. 

 35. 

 3(1 

 37. 

 38. 

 39. 

 40. 

 41. 

 42. 

 43. 

 44. 



Costa incrassate at the margin D. Arloiiis Bruk. 



— not — — 17. 



Segments almost oibieular D. inlerrupta KiTz. 



— elongate-elliiitioal D. Guinnrdiana Brun. 



Valve not constricted 19. 



— panduriforni 23. 



Valve verv convex and thick D. circiininodosa Brun. 



— not — — 20. 



Valve elliptical D. Cynthia A. S. 



— linear 21. 



Furrows decreasing in breadtli Ironi the middle D. iiiunda J,\x. 



— of eqaal breadth throughout 22. 



Central nodule small D. meditcrranea Grin. 



— — large B. contigua A. S. 



Furrow crossed hy costse D. Letoicrneurnii Cl. 



— without or witli rudimentary oostie 24. 



Gostse 4 to 7 in O.oi mm D. muscaformis Grun. 



— 7 to 8 — D. constrictn Grdn. 



— 11 to 12 — D. incurvata Greg. 



Costffi erossed by a single longitudinal rib 26. 



— several — ribs 35. 



— alternating with doiible rows of alveoli 61. 



Valve not constricted 27. 



— constricted i. ;. 29. 



L. 0,02 to 0,03 mm 28. 



L. 0,04 to 0,08 mm D. lineata UoxK. 



Furrows broad Z). discrepans A. S. 



— narrow D. Papula A. S. 



Valve gently constricted 30. 



— deeply — 34. 



Furrows decreasing in breadth from the middle D. Vctula A. S. 



— of almost ecinal breadth 31. 



Furrows very broad D. binaria A. S. 



— not — 32. 



Longitudinal rib in the middle of the stria? 33. 



— — marginal D. snbcincta A. S. 



Rib narrow D. exemta A. S. 



— broad D. demfa A. S. 



L- abont 0,o3 mm D. boiiibiforniis Cl. 



L. 0,07 to 0,1 mm D. coarctata A. S. 



Valve constricted 36. 



— not 50. 



Valve with ocelli D. areolata Cl. 



— without 37. 



Valve strongly con.stricted 38. 



— slightly — 45. 



Segments orbicular D. Clejtsydra Cl. 



— elliptical or deltoid 39. 



Costie alternating with faint alveoli D. Prtestes A. S. 



— — — distinct — 40. 



Ribs Ibrniing undulating rows D. sjjlendida Greg. 



— — straight or curved 41. 



L. 0,04 or less D. Griindleri A. S. 



L. larger 42. 



Furrows indistinct D. Weissjiogii A. S. 



— distinct 43. 



Ribs two to live on each side of the median line 44. 



— eight to ten I). Kiitzingii Gri-n. 



Transverse costie 5 to S in 0,0 1 mm £>. fiombuf! Ehb. 



— — 8 to 13 — D. chersoneiisis Grun. 



