STAURASTUUM. 157 



a few scattered, subulate, acute spines, chiefly confined to 

 the lateral extremities ; end view with three or four broadly 

 rounded angles, the spines scattered, chiefly confined to the 

 lateral extremities, sides concave. 

 Diameter 22-25 /*. 



Rhode Island, (S. T. Olney) Thwaites. 



ST. EAVENELII, Wood. Plate LVI, figs. 17, 18. Plate LXIII. 



figs. 7, 8. 



A little longer than broad ; semi-cells from the front, ellip- 

 tical or oval, not semiorbicular ; from the vertex triangular, 

 with the sides convex or slightly retuse, and the angles 

 rounded; connecting isthmus obsolete, broad sinus acute- 

 angled ; cytioderm armed with numerous acute robust spines. 

 Diameter 25-30 //. ; length 35-38 //. 



Still water, Aiken, South Carolina, collected by H. W. 

 Ravenel. 



Although in frequent correspondence with Mr. Ravenel, 

 and having examined hundreds of specimens gathered by 

 him the past years, I was not so fortunate as to find this 

 desmid until December, 1883. The specimens were dried, 

 and more or less collapsed and shriveled in consequence, but 

 I was delighted to be able to identify ten to fifteen good speci- 

 mens. A peculiarity is the somewhat irregular arrangement 

 of the conical granules. The drawing, front view, of the 

 semi cells (fig. 18) is singularly incorrect ; the inferior angles 

 should be rounded so as to form a wide, acute-angled sinus. 

 See Plate LXIII, fig. 8. 



ST. < 'ONTROVERSUM, Breb. Plate LVI, figs. 24, 25. 



Cells spinulose ; semi cells with a short, irregular process 

 on each side terminated by minute spines ; end view with 

 three or four distorted rays. 



Diameter 38-65 //.; length 75 /*., more or less. 



Marsh pool, Minneapolis, Minn. 



A variable species in size, in distortions, and in arrange- 

 ment and size of spines. The lateral angles of the semi-cells 

 are often much incurved and tipped with minute subulate 

 spines. In both views, the semi-cells show numerous conspic- 

 uous spines which are either subulate or forked at the end. 



ST. ASPixosuM, Wolle. Plate LXII, figs. 22, 23. 



Semi-cells smooth, in front view oval, with each end pro- 

 tracted into a colorless arm about three times as long as the 

 breadth of the body, diverging, apices tricuspidate, margins 



