PLATE 15. Diatoinaceae. 



The figures represent the prepared frustules or valves, except when otherwise stated. 

 Figure 



1. Pinnularia nobilis, side view. 



2. Pinnularia viridis, side view, with endochrome. 



3. Pinnularia oblonga, side view. 



4. Pinnularia radiosa, side view. 



5. Pinnularia radiosa, front view. 



6. Navicula cuspidata, side view. 



7. Navicula cuspidata, front view. 



8. Portion of the valve of a Navicula, showing the transverse rows of dots. 



9. Navicula didyma, side view. 



10. Pleurosigma balticum, side view. 



11. Hoop of the same, side view. 



12. Pleurosigma strigilis, side view. 



13. Pleurosigma hippocampus, side view. 



14. Pleurosigma acuminatum, side view. 



15. Pleurosigma attenuatum, side view. 



16. Pleurosigma attenuatum, front view. 



17. Pleurosigma Spencerii, side view. 



18. Pleurosigma lacustre, side view. 



19. Pleurosigma littorale, side view. 



20. Pleurosigma distortum, side view. 



21. Pleurosigma fasciola, side view. 



22. Pleurosigma macrum, side view. 



23. Pleurosigma prolongatum, side view. 



24. Pleurosigma tenuissimum, side view. 



25. Pleurosigma formosum, side view. 

 2.6. Pleurosigma decorum, side view. 



27. Pleurosigma obscurum, side view. 



28. Pleurosigma speciosum, side view. 



29. Pleurosigma strigosum, side view. 



30. Pleurosigma rigidum, side view. 



31. Pleurosigma elonyatum, side view. 



32. Pleurosigma delicatulum, side view. 



33. Pleurosigma angulatum, side view. , with endochrome ; b, variety (3 ; c, variety y, 



end of. 



34. Pleurosigma quadratum. 



35. Pleurosigma cestuarii. 



36. Pleurosigma intermedium. 



37. Pleurosigma, transversale. 



38. Pleurosigma transversale. 



39. Portion of valve of P. balticum. 



40. Portion of valve of P. strigosum. 



41. Portion of valve of P. angulatum (DIATOMACE^E). 



42. Portion of valve of P. littorale. 



43. Stauroneis phcenicenteron, side view. 



44. Stauroneis pulchella, side view. 



45. Stauroneis pulchella, front view. 



46. Pleurosigma angulatum, showing the dots as pearls. 



47. Isthmia enervis, portion of. 



