480 DEscBiPTioN OF IPoli/ffostrtca. 



attenuated towards each end, which is rather obtuse. Length 1- 720th. 



Sykedea virginalis. — Laterally linear, oblong, truncate, contracted 

 at the middle, dorsally lanceolate. Length 1 -600th. Genoa. 



S. constricta. — One side wider, constricted at the centre, acute at 

 each end ; the other more narrow, linear-lanceolate, and rather obtuse. 

 Length 1 -540th. Yenice. 



S. parva. — At first seen freely swimming and solitary, but at 

 length becomes attached and aggi'egated with others in a densely 

 radiating manner; laterally linear, truncate; dorsally wider, lan- 

 ceolate, acute. Length l-1200ih. In ponds free, or attached to 

 other Diatomese. 



S. dissipata. — Slender ; laterally narrowly linear, truncate ; dor- 

 sally lanceolate, acute. Length l-1140th. It probably^S./asct- 

 culata (Ehr). 



S. suhtilis=^N'avicula acus [Ehr). 



S. Famelica. — Delicate; narrowly linear, irregularly aggregated ; 

 on one side rather acute, on the other truncate. Length 1- 1020th. 

 On fresh water Algae. Halle, Germany. 



S. radians. — Delicate; very narrow, linear, veiy densely aggre- 

 gated in a radiant form ; on one side truncate, on the other attenuate 

 and sUghtly obtuse. Length 1 -600th. 



S. gmcilis. — SHghtly attached, scattered ; laterally linear, apices 

 tapering but truncate ; dorsally lanceolate, pointed, acute. Length 

 I-360th to l-240th. Marine. 



S. Fusidium. — Scattered; laterally linear, slightly attenuated at 

 the ends ; dorsally lanceolate, and somewhat acute. Length l-720th. 

 Fresh water. 



S. amphicephala. — Slender, weak, very narrow ; laterally perfectly 

 linear, truncate, dorsally tapering to the ends, which are expanded 

 (capitulate). Length 1 -360th. Fresh water, Thun. 



S. tmuissima. — Very slender and narrow, elongated; laterally 

 perfectly linear, truncate ; dorsally tapering to acute ends. Length 

 1-1 80th. Fresh water. 



S. tenuis. — Long, slender; truly linear and truncate, laterally; 

 dorsally, gradually tapering towards each end, which is rather obtuse. 

 Length l-168th. Fresh water. 



S. acicula. — Long and slender, sides gradually tapering to the ends, 



