PLATE 16.— Diatomaceje. 



Figure 



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



2. Achnanthes longipes, side view, upper valve. 



3. Achnanthes longipes, side view, lower valve. 



4. Achnanthes exilis. 



5. Achnanthidium microcephalum, side and front views. 



6. Achnanthidium flex ellum, front and side views. 



7. Amphipleura pellucida. a, side view of frustule; b, single valve ; c, Amphi- 



pleura sigmoidea. 



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



9. Amphitetras antediluviana. a, frustules united ; 6, side view ; c, front view ; 



cl, perspective view. 



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



11. Amphora membranacea, front view of single valve. 



12. Arachnoidiscus Ehrenbergii, side view. 



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



14. Bacillaria paradoxa. a, front view of conjoined frustules ; b, side view : 



c, front view of single frustule. See also PL 18. fig. 17. 



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



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



17. Cocconeis pediculus. 



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



19. Cocconema lanceolatum. 



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



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



22. Cyclotella Kutzingiana, front view. 



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



24. Cymatopleura elliptica, side view. 



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



of the same. 



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



frustule. 



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



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



single frustule. 



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



view ; c, prepared single valve. 



30. Eupodiscus argus. a, side view ; b, front view ; c, fragment, more highly 



magnified. 



31. Eupodiscus sculptus, side view. 



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



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



tules united into a filament. 



34. Gomphonema acuminatum, a, filiform stipes ; b, side view, c, front view of 



frustule. 



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



c, side view. 



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



frustule ; b, side view of variety ft ; c, sporangial frustule. 



