STAURASTRUM. 121 



St. MAJUBcuiiUM, Wblle. Plate XXXIX. 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 >>.. ; length 108-112 ft. 



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

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



Found no gelatinous sheath around any of the many speci- 

 mens examined. 



St. defectum, Breb. Plate XL. 6gs. 7-11 and 17-21. 



Semicells smooth elliptic, or extrorsely lunate with sides 



convex and end- nearly straight, c ave, "V convex ; each 



angle furnished with a longer or shorter aculeus, or awn ; 

 these are sometimes horizontal, sometimes they converge, but 

 more frequently diverge, directed obliquely upward. End 

 view triangular, or occasionally, four lobed. 



Figs. 17-21 represent the more usual forms. 



Var. mucronatum, Kail'-. Figs. 8, front view and two end views. 



Var. convergens, Wolle. Figs. 7,9, L0, II, are unusual forms 

 collected near Minneapolis, Minn.: aculei are -tout and often 

 stand nearly at right angles with the sides; they are also of 

 unusual size. 



Diameter of the various forms 2638 //. without the awns. 



A common sped. 3. 



St. MEGACANTHUM, Lund. Plate LI, figs, 10, 11, 12. 



('ell- about as long as wide (without aculei) profoundly 

 constricted; -inn- acute-angled, or subrectangular ; semicells 

 triangular-fusiform; sides somewhat convex, ends subtruncate 

 or lightly convex, angles each terminating in a strong ami long 

 aculeus; viewed from apex triangular, or rarely four lobed; 

 sides retuse; angles produced into a long and firm aculeus ; 

 membrane finely punctate. 



Diameter 50-57 //..; length about 50 a. aculei 15-18 u. 

 Pennsylvania, New Jersey, rather rare. 



St. brevispixa, Breb. Plate XL, tigs. 1,2; and Plate LIII, 

 figs. 2, 3. 

 Semicells smooth, turgid-elliptic, minutely mucronate; end 



