STAURASTRUM. 133 



St. tumidum, Breb. Plate L, figs. 1, 2. 



Large, somewhat longer than broad, deeply constricted, 

 with a distinct colorless gelatinous covering; semi-cells ellip- 

 tic or suborbicnlar ; end view bluntly triangular, sides some- 

 what convex, slightly constricted near the angles, producing 

 a nipple-like projection. Margins appear striated. 



Diameter 112 jx. 



The only habitats hitherto discovered, are marsh pools, 

 Bucks County, Pa., and Lee Pond, Mass. 



St. GRANDE, Bulnh. Plate L, figs. 3, 4. 



Large, length and breadth the same, sinuses acute, much 

 enlarged outwardly; semi -cells elliptic, angles obtuse; end 

 view triangular, rarely quadrangular, sides slightly retuse, 

 angles obtuse ; membrane finely punctate. 

 Diameter 75-83 jx. 



Marsh pools, Minneapolis, Minn. 



The specimens were some time in a weak solution of car- 

 bolic acid before being examined, and in consequence the 

 arrangement of the chlorophyl was destroyed ; omitting this 

 consideration they agree well with measures and forms de- 

 manded by the diagnosis of the author. 



St. magnum, "Wolle. Plate L, figs. 7, 8. 



Cells nearly one-third longer than broad; sinuses sub- 

 rectangular; semi-cells broad elliptic with a short, stout, 

 erect mucro at each end ; end view triangular, sides straight 

 or slightly concave, angles mucronate. 



Diameter 82 jx. ; length 100 /a. 



This species, like St. tumidum, is usually surrounded by a 

 wide, colorless, gelatinous sheath. I have this species from 

 Florida, collected by .1. D. Smith. 



It is separated from the preceding by its intermediate size, 

 proportionately greater length and the mucronate angles. 



St. majuscultjm, Wolle. Plate L, figs. 5, 6. 



Somewhat larger than St. magnum; in end view, sides not 

 concave, but convex, mucronate ; mucros not erect, but ob- 

 lique ; in front view they are curved inwardly. 

 Diameter 100-105 !x. ; length 108-112 /<. 



Two localities were productive of this form, Mt. Everett, 

 Mass., and Longwood Pond, Passaic Co., N. J. 



Found no gfelatinous sheath around any of the many speci- 

 mens examined. 



