PSEUDO-RAPHIDIEj'E. 



293 



TABLE OF COHORTS. 



Frustules really or apparently furnished longitudinally with true or false 

 septa, showing distinctly in the girdle view . . . Tabellariinese. 



Frustules with valves furnished with a carina (keel) or coarse 

 puncta, often prolonged into short costoe and with endo- 

 chrome divided transversely, or else frustules fusiform, 

 furnished with three spiral lines (carinate?), punctate . NitzscMineae. 



! Frustules 

 without 

 septa. 



Valves 

 without 

 carina. 



f Valves elliptic or circular, flat, saddle-shaped, 

 I or twisted on themselves, furnished with 



marginal aire 



Surirellinese. 



{ 



All other forms ; length of valves generally 

 much greater than the breadth, always 



without marginal alas 



I 



Fragilariinese. 



COHORT OF FRAGILARIINESE. 



ANALYSIS OF TRIBES. 



Frustules with valves more or less arcuate 



. Epithennese. 



Valves 



not 

 arcuate. 



Frustules forming long filaments, valves always without 

 pseudo-nodules ..... Fragilariese. 



Frustules 



not 



united 



into a 



filament. 



" Valves much elongated, bacillar-acicular, 



showing a false raphe and a fine striation . Synedrese. 



v , f Valves showing coarse puncta, 



rounded or square, and 

 without pseudo-nodules . Raplioneidese 



neither I 

 acicular -{ 



nor 

 bacillar 



I Valves with coarse puncta and 



[ pseudo-nodules . . Plajjiogrammese. 



Tribe VI. Epithemie^. 



' Valves furnished with beads and costae 



Valves having a central pseudo-nodule . 



Valve without terminal pseudo-nodules 



f 



Valves 



without 



costce. 



Valve 

 without 



central 

 pseudo- 

 nodules. 



. Epithemia. 

 . Ceratoneis. 

 . Pseudo-Eunotia, 



I 



Valve 



furnished 



with 

 terminal 

 nodules 



Valves with equal apices, not 



bordered with coarse beads . Eunotia 



" I 



' Valves bordered with coarse 

 beads or spines, with unequal 

 apices 



Actinella. 



