Raciborskia bicornis Woloszynska 1919, p. 199 

 PL 93, Figs. 4-7 

 Characteristics as described for the genus; cells 25-35/x long, 

 including the spines, 9-12/i, in diameter. 



Rare; attached to the aquatic moss Drepanocladus in 35 feet of 

 water; on large filamentous algae. Wis. 



TETRADINIUM Klebs 1912, p. 408 

 Cells triangular or tetrahedral, attached by a short stalk to a 

 substrate, the angles tipped with 1 or 2 short, stout spines; chromato- 

 phores many small ovate discs; nucleus central; reproduction by the 

 formation of 2 swarmers in each cell. 



Key to the Species 



Angles of the cells tipped with 2 spines T. pvanicum 



Angles of the cells tipped with 1 spine T. simplex 



Tetradinium javanicum Klebs 1912, p. 408 

 PL 93, Fig. 3 

 Cells inversely pyramidate when seen from the front, the dorsal 

 margin straight or slightly convex, the lateral margins convex, con- 

 verging to a short, stout stalk which attaches the cell to the substrate; 

 angles of the cell furnished with 2 short curved spines; cells 35-50/x 

 in diameter. 



Attached to filamentous algae. Mich., Wis. 



Tetradinium simplex Prescott in Prescott, Silva, & Wade 1949, p. 89 



PL 107, Fig. 2 

 Cells inversely triangular, sessile, with scarcely any stipe, on fila- 

 mentous algae, the dorsal margin broadly convex in front view, the 

 angles tipped with a single, downward projecting spine; triangular 

 in top view, the angles bearing a short spine; cells 12-25/x in diam- 

 eter, 12-20/x high. 



On filamentous algae in shallow water of acid ponds. Mich. 



CLASS CRYPTOPHYCEAE 



In this group the organisms are mostly motile by means of 2 apical 

 or lateral flagella (Cryptomonadales), but coccoid forms (Cryto- 

 coccales) have been placed here also. The cells are dorsiventrally 

 flattened, ovoid, slipper-shaped, or reniform, and possess a longitudi- 

 nal furrow. In some, a gullet extends inwardly from the furrow in 

 the anterior end of the cell. The pigments are dark golden-brown, 



[440] 



