STAURASTKUM. 131 



M. Eabenhoestii, Kirch. Plate LXIII, fig. 6; Plate XLV, 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, STAUEASTEUM, 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- 

 ui-ed, a complete analysis does not appear important, but for a 

 .ueneral 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 triangalar, 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. 



