l- s niA'nnrArE.K 01- \OUTII AMERICA. 



f A . ('VAinELLEJE (I.) 



B.. XAVICULEJS (II.) 



GOMPHONEME^E. (III. ) 



D AC'HNANTHEJE... (IV.) 



(E.. OoccoNiDEvK (V.) 



TEIBP] II. PSFTDO RAPHIDIF.F. 



I Frustules compound : really or apparently longitudi- 

 nally septate or vitiate: septa or vittae showing 



distinctly in f. v 1 



L Frustules not as above, or only seen in s. v. L> 



i Arcuate in f. v. .apparently .septate ?), valves alike, 

 j or differing only by a pseudo -nodule at ends of 



concave valve 9A 



L All others 9B 



/ Valves circular, sub-circular, very broadly oval, or 



-. differently costate ;! 



Valves not as above 4 



I Valves mostly hyaline, with a lew pervious costae 

 ., (scalariform . or arcuate f. v., with valves differ- 

 ently costate, really septate in f. v 9B 



1 All others 9C 



t Valves fusiform, sigmoid. or beaked, or one margin 



4. - more strongly marked than the other 9C 



I Valves not as above 5 



( Valves transversely undulate (undulations eonspieu- 



5. ; ous in f. v. , with transverse shaded bands 9( 1 



(. Valves not as above r> 



f Fi'ustules in f. v. with beaded margins (especially 



( . on one side), not ends of costae; or carinate, or 



i alate 90 



L P'rnstules not as above 7 



I Valves pervious or dimidiate, costate or striate, or 

 transvei'sely or irregularly dotted (not carinate or 



I alate) 9A 



I- Valves not as above S 



i Frustules with a row of marginal sub-capitate pro 



cesses, or alate, or carinate '. 9< ' 



(. Frustules not as above 9A 



cA FKAGILARIEYE... (\'l.) 



!>. B TABELLAEIEJE... iVII.) 



(.0 8UR1BBLLE2B (VIII.) 



