STAURASTRUM. 147 



St. eustephanum, (Ehrb.) Ralfs. Plate XLVIII, figs. 9-11. 



Of nearly equal length and breadth, granular, margins more 

 or less serrate; sernicells elliptic (fig. 9) with angles produced, 

 furcate; end view triangular, furnished with nine processes, 

 counting the three somewhat produced, and bifurcate angles ; 

 the other six are on the upper surface, attached, usually, be- 

 tween the centre and the margins, ends elevated above the 

 surface; the processes extend to margins, or slightly over 

 them ; in front view, these present themselves on the outer 

 margin in two pairs ; the third pair is either under the cell, or 

 stands towards the eye, and is invisible. 

 Diameter varies from 50-75 u, 



Var. '/. fig. I 1 represents a form with more elongated 

 processes. 



Var. b. figs, t-6 is another variety, very distinct; it is 

 smaller in size and has spreading, swallowtail-like ends of 

 processes. 



The latter was collected in Minnesota; the others occur 

 frequently in small ponds and ditches, New York, (Bailey ; 

 Ehrenberg); Pennsylvania. New .Jersey, South Carolina, 

 Massachusetts. Figs. 4-6 may represent a new species; it 

 needs further verification. 



St. senarium, (Ehrb.) Ralfs. Plate LII, fig. 1. 



Smooth, each semicell furnished with fifteen processes ; in 

 end view triangular, each angle a process, two on each side, 

 and six radiating, on the upper surface within the margins. 



I have found no form to answer this description satisfac- 

 torily. Ehrenberg and Bailey report it from New York. 



St. pseudofurcigerum, Reinsch. Plate LII, figs. 27, 28. 



Cells smooth ; sernicells broadly elliptic, sides produced 

 into a short, stout, process with margins smooth and apices 

 bifurcate ; end view triangular ; one process at each angle, and 

 two near the margin of each side, extending beyond it, making 

 nine processes to each semicell. 

 Diameter 3740 . 



Minnesota. 



I am aware that this name is usually applied to a different 

 plant, which has a granular cytioderin and margins undulate- 



