NATURAL HISTORY OF THE DIATOMACE^. 5OI 



Fig. 15. Front view of a chain of two frustules of Grammatophora marina, from the 



harbor of Salem, Mass. 

 Fig. 1 6. Front view of a filament of Melosira varians, terminated by a sporangium or 



seed vessel. From Englewood, N. J. 

 Fig. 17. Side view of Heliopelta Metii, from the marine fossil stratum of Nottingham, 



Md. The species has been lately removed from the genus Heliopelta and placed 



in Actinoptychus, and can therefore be considered as a representative of that 



genus. It is one of the most beautiful of the diatoms, and has never as yet been 



seen except in the fossil condition, and at the locality named. 

 Fig. 18. End and portion of a tube of Schizonema obtusum, from the harbor of New 



York. The little navicula-like frustules of the Schizonema are seen within the 



tube. 

 Fig. 19. A group showing both front and side view of Synedra tabulata, from the 



harbor of New York, showing the manner in which the frustules are attached to 



submerged objects by means of a cushion or short stipes. 

 Fig. 20. A chain of Diatoma vulgare, from England, showing the front view only. 

 Fig. 21. Side view of Biddulphia rhombus. From the harbor of Charleston, S. C. 

 Fig. 22. Front view of Biddulphia rhombus, showing both valves and connecting 



membrane. From the harbor of Charleston, S. C. 



Plate III. 



Fig. 23. A, B, C, D, and E, different stages of growth of Palmoglma. 



Fig. 24. Lichmophora flabellata on its stipes or stalk. From the coast of England. 



Fig. 25. Side view of JSTavicula Barklayana. From the coast of England. 



Fig. 26. Epithemia turgida, conjugating or reproducing. From England. 



Fig. 27. Side view of Pinnularia lata. From New Hampshire. 



Fig. 28. Side view of Aulacodiscus Oregonensis. From the Sandwich islands. 



Fig. 29. Side view of a JSTavicula prcBtexta. From the Gulf of Mexico. 



Fig. 30- Side view of Himantidium pectinate. 



Fig. 31. Front view of a filament of Himantidium pectinate, from a spring near New 



York. 

 Fig. 32. Side view of Meridion circulare, showing the wedge-shaped frustules united 



together so as to form a spiral. From West Point, N. Y. 

 Fig. 33. Side view of Stauroneis acuta. 

 Fig. 34. Front view of Stauroneis acuta. From England. In these two figures the 



septum, which projects like a shelf into the cavity of the frustule at the ends, can 



be seen. 

 Fig. 35. Side view of N'avicula lyra. From Germany. 

 Fig. 36. Side view of Navicula serians. From New Hampshire. 

 Fig. 37. Side view of Navicula quadrata. From Germany. 



