STATTRASTRUM. 143 



extremities; end view with three or turn- broadly rounded 

 angles, the spines scattered, chiefly confined to the lateral 

 extremities, sides concave. 

 Diameter 22-25 u. 



Rhode Island, (S. T. Oluey) Thwail 



St. Ravenelh, Wood. Plate \LV, figs. 17, 18. Plate LIP 

 figs. 7. 8. 

 A Little longer than broad ; semicells from the front, ellipti- 

 cal or oval, nol semiorbicular ; from the vertex triangular, 

 with the side- 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 u. 



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 pasl years, I was nol bo fortunate as to find this 

 desmid until December, L883. The specimens were dried, 

 and more or less collapsed and shrivelled in consequence, hut 

 I was delighted to 1"' able to identity ten to fifteen good 

 specimens. A peculiarity is the somewhat irregular arrange- 

 ment lit' the conical granules. The drawing, front view, of 

 the semicells (fig. 18 is singularly incorrect ; the inferior 

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

 -inns. See Plat. PIP fig. 8. 



St. contboversum, Breb. Plato \PY. figs. 24, 25. 



Cells spinulose ; semicells with a short irregular process on 

 each side terminated by minute spines ; end view with three 

 or four distorted rays. 



Diameter 3865 "..-, length 75 u. more or Less. 



Marsh pool, Minneapolis, Minn. 



A variable species in <i/.c, in distortions, and in arrange- 

 ment and size of spines. The lateral angles of the semicells 

 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. aspinosum, Wolle. Plate LI, figs. 22, 28. 



Semicells smooth, in front view oval, with each end pro- 



