between the lobes; apices of the lobes rounded and tipped with a 

 short, blunt spine; cells 10-15/^ in diameter, 20-30/x long. 

 Typical form not reported from our region. 



Tedraedron Victoriae var. mapr G. M. Smith 1920, p. 119 



PL 61, Figs. 28, 29 

 Cells 4-angled, divided into fusiform-shaped semicells, as seen 

 in vertical view, by deep emarginations, the two semicells bilobed 

 and cruciately arranged, each lobe produced into a stout spine; 

 cells 15-20/x in diameter, 30-60/^ long including spines. 

 Euplankter; rare but found in several lakes. Wis. 



CERASTERIAS Reinsch 1867, p. 68 

 Unicellular, free-floating, triangular or pyramidal, the angles 

 extended into long, tapering processes, the bases of which comprise 

 the body of the cell; processes all in one plane or in more than one; 

 chloroplast parietal, without a pyrenoid. 



This genus should be compared with Tetraedron, from which it 

 is separated only on relative size of the cell body. In Tetraedron 

 the main part of the cell is evident, and it may have spines or 

 processes at the angles. In Cerasterias the body of the cell is 

 practically non-existent, being only the bases of the cell lobes. 

 C. irregulare G. M. Smith is to be expected in this area, but in our 

 collections only the European species, C. staurastroides West & 

 West, has been found. It is sometimes listed as Tetraedron stauras- 

 troides (W. West) Wille. 



Cerasterias staurastroides West & West 1895b, p. 268 (fa.) 

 PI. 56, Fig. 8; PI. 61, Figs. 19, 20 



Cells tetragonal, the body narrow and gradually extended into 

 4 long, slightly tapering processes which have 2 or 4 teeth-like 

 spines (in our specimens) at the apices; the wall of the processes 

 covered with sharply pointed granules arranged in transverse series; 

 body of the cell 10/i, in diameter; greatest dimension, including 

 processes, 36.5;u. 



Our specimens differ from the typical in having the processes 

 tipped with short teeth. The apices are described as rounded by 

 Brunnthaler (1915, p. 159). 



Plankter; rare. Wis. 



POLYEDRIOPSIS Schmidle 1900a, p. 17 

 Unicellular, free-floating, tetragonal or pyramidal, the angles 

 truncately rounded and furnished with a tuft of 3-10 long, tapering 



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