Trochiscia aspera ( Reinsch ) Hansgirg 1888a, p. 128 



PI. 53, Fig. 17 

 Cells free-floating, globose, the wall moderately thick, decorated 

 with evenly distributed, wart-like projections (interconnected by 

 faint lines ?), chloroplasts several, disc-shaped; cells (13)-18-29.5^ 

 in diameter. 



Rare in plankton. Mich., Wis. 



Trochiscia granulata (Reinsch) Hansgirg 1888a, p. 128 



PI. 53, Fig. 18 

 Cells aquatic or subaerial, spherical, the wall thick and densely 

 covered with low, granular or wart-like rough enings; cells 10-20- 

 (23) /A in diameter. 

 In a Sphagnum bog. Mich., Wis. 



Trochiscia obtusa (Reinsch) Hansgirg 1888a, p. 130 



PI. 52, Fig. 8 

 Cells spherical, the wall thick, with concentric series of ridges 

 or low, parallel protuberances; 34-37;u, in diameter. 

 Tychoplankter. Mich., Wis. 



Trochiscia reticularis (Reinsch) Hansgirg 1888a, p. 129 

 PI. 53, Figs. 19, 20 

 Cells free-floating, spherical, with thick walls which are externally 

 ridged to form a reticulum in which as many as 70 polygonal areas 

 may be marked out; cells up to 39/i in diameter. 



This plant also passes under the name of T. sporoides (Reinsch) 

 Hansgirg. 



Rare; in several lakes and Sphagnum bogs. Mich., Wis. 



Trochiscia Zachariasii Leinmermann 1903, p. 157 

 PI. 53, Fig. 21 

 Cells free-floating, spherical; wall very thick and decorated ex- 

 ternally with a very coarse reticulum of prominent ridges marking 

 out 8-10 irregularly shaped, polygonal areas on the visible side of 

 the cell, forming prominent projections at the periphery; cells 10-20/i 

 in diameter. 



Rare, in plankton. Wis. 



PLANKTOSPHAERIA G. M. Smith 1918, p. 627 

 A free-floating colony of spherical cells compactly grouped within 

 a mucilaginous, homogeneous envelope; chloroplasts several, angu- 

 lar, parietal discs, each with a pyrenoid. 



[239] 



