PEDIASTRUM. 153 



Var. a. Composed of six simple cells radiately connected. 

 fig. 17. 



Var. Ik (P. Sturmii, Reinsch.) Composed of six cells, with 

 an open apace in the centre, fig. 18. 



Var. c. (P. dttodenarrus, Bailey.) fig. 2> ; composed of 

 twelve cells iii the peri | ilier\ , and a circle of four cells in the 

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



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

 -even, and four; the four constitute the centre. The openings 

 or lacunae lir-t circle -even, second four. 



The only good locality found for this species and varieties, 

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

 specimens, collected more than thirty years ago, were from 

 the same source. 



P. MTJTICUM, Kg. Plate LIII, fig. 36. 



( oenobium 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 .1. t-. y. 



P. A.NGUL08UM, (Ehrb.) Menegh. Plate LIII, figs. 28, ; >7. 



Minute, consisting of ><u<- 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 centre 

 open. 



Frequent in ponds, New Jersey. 



P. porcipatum, (Corda.) A. Br. Plate LIII, figs. 21, 30, 31. 



Coenobinin orbicular, entire, marginal cells bilobed ; lobules 

 with apices acute, converging, leaving an oval -inns between; 

 usually smooth or punctate, but sometimes coarsely granular, 

 probably when in older condition. 



Ponds, Pennsylvania, New Jersey. 



P. Boryaxum, (Turpin). Menegh. Plate LIII, figs. 22, 29, 32. 

 Coenobium orbicular, oblong or elliptic, bright green, vari- 

 able 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. Membrane punctate. 



