154 DESMIDS OF THE t;NITED STATES. 



Pond, near Minneapolis, Minn. Found no good specimens- 

 elsewhere. 



Semi-ceJIs are elliptic or fusiform, thickly spinulose. the 

 spines usually simple, rarely divided at the apex ; the semi- 

 cells taper on eauh side Into a short process tipped with three 

 or four larger aculel. 



This form agrees well with St. Saxonioum, Relnsch. Buln- 

 heim has a different form with the same name which I have 

 adopted In this monograph. 



St. teliferum, Ralfs. Plate LVI, fig. 4. 



Semi-cells more or less reniform, aculeated; the aculei 

 larger and most densely set at the angles; end view trian- 

 gular, sides concave, angles broadly rounded and bristly. 

 Diameter 33-38 m- 



Not rare In pond waters of New Jersey, Pennsylvania and 

 Massachusetts. 



St. Bkebissonii, Arch. Plate LVI, figs. 5, 6. 



Cells very near 8t. teliferum, but much larger ; semi-cells 

 more elliptic and aculei proportionately smaller. 

 Diameter 62 /u. 



Florida, the only habitat hitherto found. 



St. setigeeum, Cleve. Plate LVI, figs. 26, 27. 



Semi-cells broadly elliptic, bristly; the bristles, or more 

 properly aculei, have a firm base and sting-like apex ; they 

 are arranged on the margins, with two longer, and stronger, 

 diverging ones on each lateral angle. 

 Diameter with aculei 45 /<. ; without aculei 25 /x. 

 Not north of Florida, as far as I could discover. 



St. Saxoxicuji. Bulnh. (Not Eeinsch's form.) Plate LVI, 

 figs. 33, 34. 

 Large, spinous ; semi-cells elliptic, evenly aculeated over 

 the whole membrane ; end view triangular, sides straight or 

 slightly concave. 

 Diameter 68-75 /<. 



Budd's Lake, N. ,1. Compare note, St. acideattim. 



Var. PENTAGONUir. Plate XLII, figs. 14, 15. 



St. echinatum, Breb. Plate LVI, figs. 31, 32. 



Small, as long as broad, finely aculeated ; semi-cells 

 elliptic ; end view triangular, angles broadly rounded, sides 

 straight or lightly convex; whole membrane except the 



