STAURASTKUM. 131 



M. EABENHORSTII, Kirch. Plate LXIII, fig. 6; Plate XL V, fig. 6. 



Cells as long as broad, small, three lobed ; terminal cell 

 not much wider than the lateral lobes, widened from the 

 base to the end, apex concave, angles terminating with two 

 short teeth ; lateral lobes divided by a wide, almost right- 

 angled sinus, each half somewhat narrowed towards the 

 end ; apex indented, a small tooth at each angle. Mem- 

 brane smooth. 



Thus reads a free translation of Kirchner's diagnosis. 

 The figure does not represent the type ; merely a small form 

 of it. 



Diameter 62-85 /<. 



Collected in ponds in the vicinity of Minneapolis, Minn. 



Genus, STAURASTKUM, Meyen. 



Cells in front view similar to Cosmarium, end view, three to six 

 or more, angular ; angles obtuse, acute', or drawn out into elon- 

 gated horn-like processes. Chlorophyl more or less concentrated 

 into a central mass, margins radiating towards the margins of the 

 semi-cells. Zygospores provided with spines. 



This genus contains a large number of species; as all are fig- 

 ured, a complete analysis does not appear important, but for a 

 general guide they may be divided into four larger sections, in 

 the order observed in the following list: 



SECTION I. Membrane of cells smooth, or rarely punctate or indistinctly gran- 

 ular. 



SECTION II. Membrane verrucose, or rough with pearly granules. 



SECTION III. Membrane hairy, spinulose or aculeated. 



SECTION IV. Membrane with angles extended into arms, or horn-like processes. 



SECTION I. 



ST. MUTICUM, Breb. Plate L, figs. 11-15. 



Cells in front view orbicular, smooth, deeply constricted, 

 often involved in a mucous envelope ; semi-cells elliptic; end 

 view triangular, or rarely quadrangular: angles rounded, 

 sides slightly concave. 



Diameter 33-38 /*. Frequent. 



Var. MINUS (figs. 14, 15) does not differ from the typical form 

 except in size ; measures only about one-half. 



