STAURASTRUM. 41 



M. VERRUCOSA, Eoy. Plate LIX, fig. 10. 



Iii outline this species agrees with smaller forms of M. 

 denticulate^ Ealfs, but differs from these and other described 

 forms by the remarkable row of crenulated, circular or oval 

 basal inflations, crossing from side to side, larger towards 

 the center, gradually growing smaller towards the margins. 



The original type was found in Scotland. The first from 

 this country is from a pond near Minneapolis, Minnesota, 

 in collections made by Miss E. Butler. 



M. RINGENS, Bail. V. Des. U. S. p. 112, var. SERULATA, 



Wolle. Plate LIX, fig. 15. 



In size and form the same as the original type from 

 Florida. Bailey describes it as " granular near the mar- 

 gins," but not as serrated. This new variety has the 

 margins distinctly serrated, besides having the granules or 

 mucros near the margins. 



Diameter 115-130 ^ ; length 125-145 /*. 



Found in large numbers in White Bear Lake, Minnesota, 

 by Miss E. Butler. 



Genus, STAUEASTEUM. V. Des. U. S. p. 119. 



ST. MUTICUM, var. ELLIPTICUM. Plate LX, figs. 41, 42. 



A form differing from that of Plate XXXIX, and more 

 strictly elliptical, semi-cells in front view slightly con- 

 tracted near the ends. 



Diameter 33-35 //. 



Pond, St. Anthony Park, Minneapolis, Minnesota. 



ST. ORBICULARE. V. Des. U. S. p. 119. 



A variety from Watertown, New York. Plate LX, figs. 

 36-38, not so distinctly orbicular as the form illustrated, 

 Plate XXXIX, figs. 9, 10. 



Diameter 34-37 ju ; length about 44 yw. 



ST. BACILLARE, Breb. Plate LVII, figs. 5, 6. 



Cells small, deeply constricted, sinus a wide, acute angle ; 

 semi -cell narrow lanceolate, base convex, ends inflated, 

 head -like, in vertical view 3-4-5 - angled ; angles radiately 

 produced with ends enlarged and rounded. 



Diameter 25-30 /<. 

 Pond, Minnesota. 



