124 DESMIDS OF THE UNITED STATES. 



St. commutatum, Kg. Plate XL, figs. 33, 34. 



Smooth or punctate-granulate ; semicells diverging, obverse 

 semilunar; base broadly rounded, ends straight or somewhat 

 concave; apices bifid; end view triangular, angles produced 

 and apices bicuspidate; sides moderately retuse. 



Diameter 35-38 ;i. omitting the spines. 



Pond, Lehigh Valley, Pennsylvania. 



This form may not be strictly the plant described by the 

 author, Kutzing ; it is near it, and appears to stand between it 

 and ^4. Bulnheimianum, Rab. Have seen very few of them, 

 hence record the name merely provisionally. 



9t. brachiatum, Ralfs. Plate XL, fig.-. 37,38,39; and Plate 

 LI I, figs. 29, 30, 31. 

 Cells smooth; semicells with three diverging processes, 

 or according to other authors, 2-4-5 radiate, which are deeply 

 bifid or tritid at the apex ; end view with three or four rays. 



Diameter 3355 fi. Not frequent. 



The figures od Plate LII, represent a form noted as variety 

 Notarisii, Pah. Collected in ponds Bamber and Brown's 



Mills, N. J. 



St. paniculosum, Wnlle. Plate XLI, figs. 39, 40. 



Cell hexangular, as long as broad, membrane punctate ; 

 punctules in radiating lines ; semicells truncated triangles, 

 angle.- rounded ; inferior angles furnished with two short, 

 straight aculei : end view triangular with one small aculeus 

 visible on each rounded angle; sides moderately convex. 



Diameter 40-50 fi. 



Marsh pools, near Bethlehem, Pa. 



St. Bieneam'm, Rab. Yar. ellipticum, Wille. Plate \ LII, 

 figs. 1, 2. 

 Semicells elliptic : end view triangular with angles rounded, 

 sides more or less deeply concave ; membrane finely punctate, 

 distinctly observable when the cell is empty ; punctules regu- 

 larly arranged in transverse Lines. 

 Diameter 33-38 u. 



Net numerous, but hitherto found specimens in Minnesota, 

 Massachusetts, New Jersey, Pennsylvania and Florida. 



