PEDIASTRUM. 169 



Var. c. (P. duodenarius, Bailey), fig. 20; composed of 

 twelve cells in the periphery, and a circle of four cells in the 

 middle, with open spaces between the two, and open center. 

 Var. d. A new form, with three circles of cells, of four- 

 teen, seven, and four ; the four constitute the center. The 

 openings, or lacunae, first circle seven, second four. 



The only good locality found for this species and varieties 

 is the Croton water supply of the City of New York. Bailey's 

 specimens, collected more than thirty years ago, were from 

 the same source. 



P. MUTICUM, Kg. Plate LXIV, fig. 36. 



Coenobium circular or oval, composed of two to five circles 

 of cells, entire, smooth, regular ; peripheric cells emarginate 

 or with two slight protuberances. 



Pond waters, Pennsylvania, New Jersey. 



P. ANGULOSUM, (Ehrb.), Menegh. Plate LXIV, figs. 28, 37. 



Minute, consisting of one or more circles of cells. Not 

 perforated ; marginal cells with angular lobes which are not 

 extended into rays. A small form (fig. 37) has the center 

 open. 



Frequent in ponds, New Jersey. 



P. FORCIPATUM, (Corda.), A. Br. Plate LXIV, figs. 21, 30, 31. 

 Coenobium orbicular, entire, marginal cells bilobed ; 

 lobules with apices acute, converging, leaving an oval sinus 

 between; usually smooth or punctate, but sometimes coarsely 

 granular, probably when in older condition. 

 Ponds, Pennsylvania, New Jersey. 



P. BORYANUM, (Turpin), Menegh. Plate LXIV, figs. 22, 29, 32. 



Coenobium orbicular, oblong or elliptic, bright green, 

 variable in size, composed of 8-16-128 cells. Marginal cells 

 two lobed, each drawn out into a colorless horn-like process, 

 short or long, rather obtuse, sometimes a little thickened at 

 the ends- Cells closely united, four to six angled. Mem- 

 brane punctate. 



Sometimes the cells and the horns are distinctly granulate. 

 These constitute the variety granulatum, Kg. 

 Frequent, Massachusetts to Florida. 



P. PERTUSUM, Kg. Plate LXTV, figs. 33, 34. 



Coenobium, more or less orbicular, pierced with many 

 lacunae ; variable in size ; composed of 16-32-64 cells. All 

 the cells more or less loosely connected ; attached at the 

 angles only, leaving an opening between the sides, and be- 



