FRESH-WATER ALG^ OF THE UNITED STATES. 153 



Segments in f. v. triangular, ends truncate, rough with minute granules, tapering at each side 

 into elongate, straight, slender, horizontal processes, terminated by three or four minute 

 spines ; e. v. triradiate, processes straight, sides concave. (A.) 



C. CyTIODERMA PILOSXIM, SPINTJLOStTM VEL ACULEATUM. 



Cttiodekm pilose, spinulose ok thorny. 



St. polytrichum, Perty. 



St. mediocre, tam longum quam latum, profunde constrictum, sinu acutangulo ampliato, super- 

 ficie undique setosum ; semicellulis ellipticis vel snbellipticis, divergentibus, dorso subplanis, 

 ventre tumidis, margine setoso-ciliatis, a vertice triangularibus, angulis obtusis, lateribus 

 subrectis. (R.) 



Diam.~jl^^" = .0011". 



Syn. — St. polytrichum, Pertt. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 214. 



Hab. — Prope Philadelphia ; Wood. 



Moderately large, about as long as broad, profoundly constricted, with the acute angled sinus 

 widened, surface everywhere furnished with setse ; semicells elliptical or subelliptical, diver- 

 gent, the dorsum nearly plane, their belly swollen, the margin setose -ciliate, from the vertex 

 triangular, the angles obtuse. 



Bemarks. — This desmid appears to be rare in. this country, as it probably is also 

 in Europe. I have seen but a single specimen, which I found amongst other algse 

 near Chelten Hills, north of the city. It agreed in all respects with the descrip- 

 tion of Rabenhorst, as given above. 



Fig. 12, pi. 13, is a drawing of this plant, also fig. 23, pi. 21. 



St. BaTenelii, Wood. (sp. nov.) 



St. mediocre, paulo longius quam latum ; semicellulis a fronte ellipticis, a vertice triangularibus 

 cum lateribus convexis vel leniter retusis et angulis rotundatis ; isthmo connexivo subnullo, 

 lato ; sinu acutangulo ; cytiodermate spinis acutis, robustis numerosis armato. 



Diani.—Long. T3jTn,„" = 0.0014". Lat. -rTyVir" = O-OOl"- 



Sab. — South Carolina ; (Ravenel) Wood. 



Mediocre, a little, longer than broad ; semicells from the front elliptical, from the vertex trian- 

 gular, 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. 



Bernard. — Fig. 22, pi. 21, represents the front view of an empty frond of this 

 plant ; fig. 22 a, the side view, and fig. 22 b, the end, aU magnified 750 diameters, 



St. hirsutntn, (Ehrb.) Breb. 



St. magnum, tertiam partem circiter quam longius quam latum, plus minus dense spinulosum, 



sinu plus minus lineari, acutangulo; semicellulis late ellipticis vel subsemiorbicnlaribus, 



spinis tenuibus strictis hirsutis, a vertice triangularibus, angulis obtuse rotundatis, lateribus 



rectis vel leniter convexis. (R.) Species mihiignota. 



Biam.— Sine spinis 0.0015". Zygospor. 0.0022". (R.) 



Syn.— St. Ursutum, (Ehrenberg) Br^bisson. Rabenhorst, Flora Europ. Algarum, Sect. 



III. p. 211. 

 Sj6.— Florida; Rhode Island; Bailey. Rhode Island; (S. T. Olney) Thwaites. 



20 August, 1872. 



