154 DESMIDS OF THE UNITED STATES. 



Pond, near Minneapolis, Minn. Found no good specimens 

 elsewhere. 



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

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

 cells taper on ea-^h side into a short process tipped with three 

 or four larger aculei. 



This form agrees well with St. Saxonicum, Reinsch. Buln- 

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

 adopted in this monograph. 



ST. TELIFERUM, Ealfs. 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 //. 



Not rare in pond waters of New Jersey, Pennsylvania and 

 Massachusetts. 



ST. BREBISSONII, Arch. Plate LVI, figs. 5, 6. 



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

 more elliptic and aculei proportionately smaller. 

 Diameter 62 /<. 



Florida, the only habitat hitherto found. 



ST. SETIGERUM, 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 yw. ; without aculei 25 //. 

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



ST. SAXONICUM, Bulnh. (Not Reinsch' 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 n. 



Budd's Lake, N. J. Compare note, SY. >-n!< aiinn. 



Var. PENTAGONUM. 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 



