PLATE 15. — Diatomaceae. 



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. Navicida cuspidata, side view. 



7. Navicida cuspidata, front view. 



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



9. Navicida 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. 



26. Pleurosigma decorum, side view. 



27. Pleurosigma, obscurum, side view. 



28. Pleurosigma speciosimi, side view. 



29. Pleurosigma strigosum, side view. 



30. Pleurosigma rigidum, side view. 



31. Pleurosigma elongatum, side view. 



32. Pleurosigma delicatulum, side view. 



33. Pleurosigma angidatum, side view, a, with endochrome ; b, variety ft ; c, varietyy, 



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. angidatum (Diatomace^;). 



42. Portion of valve of P. littorale. 



43. Stauroneis phoenicenteron, side view. 



44. Stauroneis pulchella, side view. 



45. Stauroneis pulchella, front view. 



46. Pleurosigma angulation, showing- the dots as pearls. 



47. Isthmia enervis, portion of. 



