PLATE 12.— Diatomaceae. 



Figure 



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



2. Achnanthes longipeSy side view, upper valve. 



3. Achnanthes longipes, side view, lower valve. 



4. Achnanthes exilis. 



5. Achnanthidium microcephalum, side and front views. 



6. Achnanthidium Jlexellumy front and side views. 



7. a,y Amphipleura pellucida, side view of frustule; 6, Amphipleura pellucida, single 



valve ; c, Arnphipleura sigmoidea, 



8. Amphiprora alata. «, side view ; 5, front view. 



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



d, perspective view. 



10. Amphora ovalis, front view ; ]0«, transverse section. 



11. Am'phora memhranacea ; front view of single valve. 



12. Arachnoidiscus Ehrenhergiiy side view. 



13. Arachnoidiscus Ehrenbei^gii, portion of valve from the centre to the circumference. 



14. Bacillaria paradox a. ay front view of conjointed frustules; 6, side view; 



Cy front view of single frustule. 



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



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



17. Cocconeis pediculus. 



18. Cocconeis scutellumy single valve (side view). 



19. Cocconema lanceolatum. 



20. Cocconema lanceolatuMy single valve (side view). 



21. Cyclotella operculata, a, side view; 6, front view. 



22. Cyclotella Kutzingianay front view. 



23. Sphinctocystis solea. ay side view; 5, front view. 



24. Sphinctocystis ellij)ticay side view. 



25. Denticula obtusa. by front view ; c, side view of single frustule ; c?, front view 



of the same. 



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



frustule. 



27. Diadesinis confervacea. a, front view ; 5, side view. 



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



single frustule. 



29. Do?yphora amphiceros. a, side view of frustule with endochrome ; 6, front 



view ; c, prepared single valve. 



30. Eupodiscus argus, a, side view ; by front view. 



31. Eupodiscus sculptus, side view. 



32. Epithemia turgida. ay 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, by side view ; c, front view of frustule. 



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



Cy side view. 



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



tule ; by side view of variety /3 ; c, sporangial frustule. 



