colorless, somewhat twisted horns, one of which is recurved and is 

 directed at an angle from the longitudinal axis; protoplast forming 

 2 ( or only 1 ) Gymnodinium-hke swarmers which have a wide trans- 

 verse furrow, dividing the zoospore into a broadly rounded anterior 

 portion and a broadly conical or sharply pointed posterior, with 

 pigment-spot showing in the longitudinal furrow; cells 28-36/^ in 

 diameter, 40-60/x long (sometimes longer); swarmers about 20/x 

 in diameter, 25^ long. 



In the tychoplankton of several lakes and swamps; frequently 

 found in desmid habitats. Wis. 



Cystodinium iners Geitler 1928a, p. 5 

 PL 91, Figs. 19-21 



Cells crescent-shaped, strongly convex on the dorsal margin, 

 tumid (or straight) on the ventral or inner margin, ending in sharp 

 points at the poles, with the wall much thickened at the base of the 

 horns, which are in the same plane with the longitudinal axis of the 

 cell; protoplast usually showing a transverse furrow, appearing as 

 a Gymnodinium-\ike cell dividing to form two swarmers; chromato- 

 phores numerous ovoid plates; cells 25-28-(30)ai in diameter, 60-80^ 

 long, including the apical spines. 



Mich.,Wis. 



Cystodinium Steinii Klebs 1912, pp. 382, 442 

 PI. 93, Figs. 1, 2 



Cells crescent-shaped, the dorsal margin more strongly convex 

 than the ventral; apices terminating in curved and shghtly twisted 

 points, each projecting at a different angle from the longitudinal 

 axis of the cell; upon dividing producing 2 Gymnodinium-\ike 

 swarmers with a broad transverse furrow and with both poles 

 broadly rounded; pigment-spot in the longitudinal furrow; cells 

 25-35/x in diameter, 65-100- (1 10 )At long; swarmers 30-35/. wide, 

 40-50/. long. 



Rare; in the tychoplankton of lakes and acid swamps. Mich., Wis. 



RACIBORSKIA Woloszynska 1919, p. 199 



Cells attached, inversely triangular-ellipsoid as seen from the 

 front, ellipsoid when seen in vertical view, the poles tipped with a 

 single stout spine; attached by a short stalk to the substrate; in side 

 view the upper margin straight, the 2 lateral margins straight or 

 shghtly convex, converging to the thick stalk; reproduction (?). 



[439] 



