DIATOMACEJE. 



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DIATOMACEvE. 



v. circular, equal, punctate or striate, 

 with a fringe of minute marginal 

 teeth ; freshwater (PI. 18. figs. 26, 27, 

 28, 29). 



Stephanogonia. Fr. as in Mastogonia, 

 but ends of valves truncate, angular, 

 and spinous ; fossil (PI. 18. fig. 30). 



Hercotheca. Fr. single, turgid laterally ; 

 v. with marginal free setae (PL 18. 

 fig. 31). 



Ooniothecium. Fr. single, constricted in 

 the middle, suddenly attenuate and 

 truncate at the ends (hence appearing 

 angular) (PI. 51. figs. 18-23).] 

 Coh. 5. SUBIRELLE.^ Fr. single or binate, 

 quadrilateral, oval, or saddle-shaped, 

 sometimes constricted in the middle; 

 v. with transverse or radiating conti- 

 nuous or granular striae, interrupted in 

 the middle, or with one or more longi- 

 tudinal rows of puncta ; often keeled. 



BaciUaria. Fr. prismatic, straight, at 

 first forming a filament ; v. with a me- 

 dian longitudinal row of puncta ; ma- 

 rine (PL 16. fig. 14). f 



Campylodiscus. Fr. single, free, disk- 

 shaped ; v. curved or twisted (saddle- 

 shaped) ; freshwater and marine (PI. 16. 

 fig. 16; PI. 25. fig. 18). 



Doryphora. Fr. single, stalked ; v. lan- 

 ceolate or elliptical, with transverse 

 granular strise (PI. 16. fig. 29). 



Podocystis. Fr. attached, sessile ; y. with 

 a median line, transverse-continuous 

 and intermediate granular striae (PI. 61. 

 fig. 7). 



Nitzschia. Fr. free, single, compressed, 

 usually elongate, straight, curved or 

 sigmoid, with a not-median keel, and 

 one or more longitudinal rows of 

 puncta ; freshwater and marine (PI. 17. 

 figs. 9-13). 



Cymatopleura (Sphinctocystis). Fr. free, 

 single, linear, with undulate margins ; 

 v. oblong or elliptical, sometimes con- 

 stricted in the middle; freshwater 

 (PL 16. figs. 23, 24). 



Surirella. Fr. free, single, ovate, ellipti- 

 cal, oblong, cuneate, or broadly linear ; 

 v. with a longitudinal median line or 

 clear space, margins winged, and with 

 transverse or slightly radiating con- 

 tinuous striae ; freshwater and marine 

 (PL 17. figs. 21-22). 



(Plagiodiscm.') 



Synedra. Fr. prismatic, rectangular, or 

 curved; at first attached to a gelati- 

 nous lobed cushion, often becoming 



free; v. linear or lanceolate, usually 

 with a median pseudo-nodule and lon- 

 gitudinal line ; freshwater and marine 

 (PL 17. figs. 23-25). ^ 



Tryblionella. Fr. free, linear or elliptical ; 

 v. plane, with a median line, transverse 

 striae, and submarginal or obsolete alae ; 

 freshwater and marine (PL 17. figs. 

 30-32). 



Rhaphoneis=. Doryphora without a stalk. 

 Coh. 6. AMPHIPLEUBE^:. Fr. free, single, 

 straight or slightly sigmoid ; v. lanceo- 

 late, or linear-lanceolate, with a median 

 longitudinal line. 



Amphipkura. Char, as above (PL 16. 

 fig. 7 a, b, c). 



Oylindrotheca (PL 51. fig. 34). 



ft Valves with a median nodule. 



Coh. 7. COCCONEHXE. Fr. straight or bent, 

 attached by the end or side; valves 

 elliptical, equilateral. 



Cocconeis. fr. single, compressed, ad- 



nate ; v. elliptical, one of them with a 



median line (PL 16. figs. 17, 18). 



Coh. 8. ACHNANTHE.S:. Fr. bent, stalked 



at one angle or free ; v. with a stauros. 



Achnanthes. Fr. compressed, single or 

 rarely united into a straight filament, 

 curved, attached by a stalk at one 

 angle ; uppermost valve with a longi- 

 tudinal median line, lowermost with 

 the same, and a stauros or transverse 

 line ; marine (PL 16. figs. 1-4). 



Achnanthidium. Fr. those of Achnanthes, 

 but free; freshwater (PL 16. figs. 5, 6). 



Cymbosira. Fr. those of Achnanthes, so- 

 litary or binate, stipitate, and attached 

 end to end ; marine (PL 19. fig. 18). 

 Coh. 9. CYMBELLE-as. Fr. straight or 

 curved, free or stalked at the end ; 

 v. inequilateral, not sigmoid. 



CymbeUa. Fr. free, solitary; v. na- 

 vicular, with a subcentral and two 

 terminal nodules, and a submedian 

 longitudinal line ; freshwater (PL 51. 

 fig. 2). 



Cocconema. Fr. those of CymbeUa, but 

 stalked; freshwater (PL 16. figs. 19. 

 20). 



Coh. 10. GOMPHONEME^;. Fr. wedge- 

 shaped, straight, free or stalked; v. 

 equilateral. 



Gomphonema. Fr. single or binate, 

 wedge-shaped, attached by their ends 

 to a stalk ; v. with a median line, and 

 a median and terminal nodules ; fresh- 

 water (PL 16. fig. 34). 



