STAUKASTRUM. 163 



ST. SPONGIOSUM, Breb. Plate LVIII, figs. 5-8. 



Thickly covered with short spines which are forked at the 

 apex ; semi-cells semiorbicular, spinulose ; end view trian- 

 gular, angles rounded ; sides slightly convex and bordered 

 with forked spines or short processes. 

 Diameter 45-50 jn. 



This species appears to be sparsely but widely distributed. 

 The specimens vary considerably in different localities ; figs. 

 7, 8, represent the more frequent form ; Naegeli supposed it 

 to be a new species and named it St. Griffitheanum. 



ST. ARCTISCON, Ehrb. Plate LVIII, figs. 9, 10. 



Cells about one-fourth longer than broad, moderately con- 

 stricted, sinuses obtuse angled; semi-cells subglobose, slightly 

 depressed, furnished in the middle with (usually) nine 

 straight divergent processes ; above these another whorl con- 

 sisting, usually, of six similar, but shorter processes, apices 

 trifid. Membrane punctate. 



Diameter 100-120 ,w. 



In addition to the forms represented on Plate LVIII, figs. 

 {), 10, I add another, apparently more highly developed, Plate 

 XLVI, fig. 4, distinct in the large, wide-spreading points of 

 the trifid apices of the arms. 



Green Lake and other waters of New Jersey. 



Wood describes St. munitum as a new species, but evidently 

 it is the same as St. arctiscon. He had it from New Hamp- 

 shire ; I found it frequently in Massachusetts, Pennsylvania, 

 New Jersey. No doubt it will turn up in all parts of the 

 United States. Ehrenberg had his specimens from New York. 



ST. WOLLEANUM, Butler. Plate XLVIII, 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 pro- 

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

 similar processes within the margin ; in vertical view regular 

 hexagonal, each angle furnished with an arm in appearance 

 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. 



