NITZSCH1A. 



)83 



Table of Groups. 



f Striae in quincunx ; valve broad, constricted at the median portion 



4; 



, bfl 



i C 



o 



( 



s. 



L 



Valve f 

 showing 

 undula- -\ 

 tions or 

 hollows. [_ 



r 



Valve linear, longly lanceolate or longly elliptic ; striae very distinct 

 Valve very broadly lanceolate ; transverse stria- very fine and indistinct 



Valves showing costre 



more or less 



dimidiate or carinal 



dots prolonged into 



delicate costrv. 



o 



5'5 



5 S 



J) m 

 3 if 



*- Si 



m zj 

 3 ^- 



Keel 



! straight, not 



inflected at 



the median 



portion. 



\ Costae dimidiate, robust 



I 



( Frustules straight 

 I Costae ) 

 I delicate. J Frustules spathulate or somewhat sig- 



V moid . 



f Keel almost central ; girdle face with apices not 

 attenuate ..... 



Keel eccentric ; girdle face with apices very slightly 

 I. attenuate . . . 



Valve 

 not 



undulated. 



Keel eccentric, inflected at the median portion 



I Valves arcuate . . . . . 



Keel accompanied by two longitudinal parallel lines 



' Girdle f 



face J Keel eccentric ; girdle face not broad 



-a 

 '5 

 E 

 to 



2. *Panduriformes. 



1. Tryblionella. 

 5. Circumsutse. 



9. Grunowia. 



10. Scalares. 



11. Insignes. 

 1G. Sigmoideae 



17. Sigmata. 



18. Obtusse. 



19. Spectabiles. 

 14. Spathulatae. 



con- 

 stricted 

 in the 

 middle. 



6. Dubise. 



i Keel slightly eccentric; girdle face very broad 7. Bilobatse. 



f Carinal dots somewhat prolonged 



13. Vivaces. 



Girdle 

 face not 



con- 

 stricttvl 



in the 

 median 

 portion. 



Valves showing a longitudinal sulcus in 

 which the striae are absent or feeblv marked 3. Apiculatse. 



to 



S. 



o _ 



{ Keel quite eccentric 



Keel almost central ; striae 

 very distinct ; frustules uni- 

 ted into a stratum 



o 



Hi 



21. Lanceolatse. 



U 



I 



I 



12. Bacillaria. 



3 I 2 - 



to ;r 



_5 



c 

 Z 



u 

 I -J, I 



Keel some- 

 what 

 eccentric ; 

 frustules .j y ^ y(S lanceQ 

 not united 

 into 

 strata. 



Valves linear, 

 lirge ; striae 

 distinct . 20. Lineares. 



I 



I Valve very longly rostrate and with a very eccentric keel 



late, very 

 small ; striae 

 indistinct . 15. Dissipatse. 



22. Nitzschiella. 



* The figures correspond with those of the groups in H.V.H. Atlas; the missing numbers (4. Pseudo-Tryblionella 

 and 8. Epithemioideae) are those of groups which are not represented in Belgium or England. 



