PLATE 12. Diatomacese. 



Figure 



1 . Achnanthes longipes, the front view of the frustules is visible. 



2. Achnanthes longipes y side view, upper valve. 



3. Achnanthes longipes y side view, lower valve. 



4. Achnanthes exilis. 



5. Achnanthidium microcephalum, side and front views. 



6. Achnanthidium flexellum, front and side views. 



7. a, Amphipleura pellucida y side view of frustule; b y Amphipleura pellucida, single 



valve ; c, Amphipleura sigmoidea. 



8. Amphiprora alata. a, side view ; b, front view. 



9. Amphitetras antediluviana. a, frustules united ; b y side view ; c, front view ; 



d, perspective view. 



10. Amphora ovalis, front view ; 100, transverse section. 



11. Amphora membranacea ; front view of single valve. 



12. Arachnoidiscus Ehrenbergii y side view. 



13. Arachnoidiscus Ehrenbergii, portion of valve from the centre to the circumference. 



14. Bacillaria paradoxa. a y front view of conjointed frustules; b, side view; 



c, front view of single frustule. 



15. Biddulphia pulchella, front view. , frustule dividing, front view. 



16. Campylodiscus costatus, side view, b, front view. 



1 7. Cocconeis pediculus. 



18. Cocconeis scutellum, single valve (side view). 



19. Cocconema lanceolatum. 



20. Cocconema lanceolatum, single valve (side view). 



21. Cyclotella operculata. a, side view; b, front view. 



22. Cyclotella Kutzingiana y front view. 



23. Sphinctocystis solea. a, side view; b, front view. 



24. Sphinctocystis elliptica y side view. 



25. Denticula obtusa. b, front view ; c, side view of single frustule ; d y front view 



of the same. 



26. Diatoma vulgare y connected frustules. a y side view; b, front view of single 



frustule. 



27. Diadesmis confervacea. a y front view ; b y side view. 



28. Meridion constrictum. a y connected frustules forming a coil ; b y front view of 



single frustule. 



29. Doryphora amphiceros. a y side view of frustule with endochrome ; b y front 



view ; c, prepared single valve. 



30. Eupodiscus argus. a y side view ; b, front view. 



31. Eupodiscus sculptus y side view. 



32. Epithemia turgida. a y side view ; b, front view. 



33. Fragilaria capucina; side view of frustule, front view of the same, and frustules 



united into a filament. 



34. Gomphonema acuminatum. b y side view; c y front view of frustule. 



35. Grammatophora marina, connected frustules. b, single frustule, front view ; 



c y side view. 



36. Himantidium pectinale, united frustules, front view, a, side view of single frus- 



tule ; b, side view of variety @ ; c, sporangial frustule. 



