44 FRESH-WATER ALGJE OF THE UNITED STATES. 



011 each side of the triangle ; around the center are nine 

 more spines, often indistinct. 



Diameter 65-75 JJL without, and 90-100 /< with the spines. 

 Frequent in Minnesota ponds. 



ST. XIPHIDIOPHORUM, Wolle. Plate LYII, figs. 21, 22, and 



Plate LX, fig. 19. 



Small, one and one-half to two times as long as broad, 

 deeply constricted, sinus narrow, widening irregularly out- 

 wardly ; semi-cells transversely oblong, with lateral margins 

 notched ; the end margins drawn out into a sort of one-sided, 

 hastate, poignard-like spines or slender points, usually nine 

 in number ; membrane smooth ; with several verrucae j end 

 view triangular, angles broadly truncate and usually each 

 showing three prominences, the bases or supports of three 

 spines, sides concave. 



Diameter 25-30 ju ; length 40 ju, and upward. 



Ponds, near Minneapolis and Stillwater, Minnesota. 



Var. SIMPLEX, Wolle, differing from the type-form in having 

 less spines, usually six ; (Plate LX, fig. 19,) in end view the 

 truncate angles have only two prominences each. 



Found this form frequent in material collected in small 

 pools near Lake Tahoe, California, by Mrs. Hanson and Miss 

 Haggin, of San Francisco. 



ST. WOLLEANUM, Butler. Plate LYII, figs. 1, 2. 



Medium size, membrane punctate, about one-half longer 

 than broad, moderately constricted, sinuses obtuse-angled ; 

 semi- cell broadly oval or subhexagonal ; superior and lateral 

 angles produced into subcylindrical, somewhat swollen 

 processes or arms, slightly notched at the apices ; four more 

 similar processes within the margin ; in vertical view regu- 

 lar hexagonal, each angle furnished with an arm in appear- 

 ance as those in front view ; within the margin, arranged in 

 a circle around the center, are six, more or less conspicuous 

 processes. 



Diameter of body 40-50 /* ; with processes 65-83 //. 



This species was discovered, identified as new and named 

 by Miss E. Butler, Minneapolis, Minnesota, where it was 

 found. 



Var. KISSIMMENSE, Wolle. Plate LIX, figs. 1, 2, 3. 



Front, lateral and vertical views. A large, smooth and beau- 

 tiful form fully one-half larger than the original type from 



