144 THE MICROSCOPIST. 



21. Goniothecium. JBY. single, constricted in the middle, 

 suddenly attenuate and truncate at the ends (hence appear- 

 ing angular). 



COHORT 5. SURIRELLE.E. Fr. single or binate, quadri- 

 lateral, oval, or saddle-shaped, sometimes constricted in 

 the middle; v. with transverse or radiating continuous 

 or granular striae, interrupted in the middle, or with one 

 or more longitudinal rows of puncta; often keeled. 



22. Bacillaria. Fr. prismatic, straight, at first forming 

 a filament; v. with a median longitudinal row of puncta; 

 marine. 



23. Campylodisciis. Fr. single, free, disk-shaped; v. 

 curved or twisted (saddle-shaped); aquatic and marine. 



24. Doryphora. Fr. single, stalked; v. .lanceolate or 

 elliptical, with transverse granular striae. 



25. Podocystis. Fr. attached, sessile; v. with a median 

 line, transverse continuous, and intermediate granular 

 striae. 



26. Nitzschia. Fr. free, single, compressed, usually elon- 

 gate, straight, curved, or sigmoid, with a not-median 

 keel, and one or more longitudinal rows of puncta ; 

 aquatic and marine. 



27. Sphinctocystis (Cymato pleura). Fr. free, single, linear, 

 with undulate margins; v. oblong or elliptical, sometimes 

 constricted in the middle; aquatic. 



28. Surirella. Fr. free, single, ovate, elliptical, oblong, 

 cuneate, or broadly linear; v. with a longitudinal median 

 line or clear space, margins winged, and with transverse 

 or slightly radiating continuous striae ; aquatic and marine. 



29. Synedra. Fr. prismatic, rectangular, or curved ; at 

 first attached to a gelatinous-lobed cushion, often becom- 

 ing free; v. linear or lanceolate, usually with a median 

 pseudo-nodule and longitudinal line ; aquatic and marine. 



30. Tryblionella. Fr. free, linear, or elliptical ; v. plane, 

 with a median line, transverse striae, and submarginal or 

 obsolete alae ; aquatic and marine. 



