FRESH-WATER ALG^ OF THE UNITED STATES. 153 



Segments in f. v. triangular, ends truucato, 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 pilosum, spinulosum vel aculeatum. 



CyTIODER.M pilose, SPINULOSE or THORNy. 



St. polyfcichiiin, Perty. 



St. mediocre, tarn longuni quani latum, profunde constrictura, sinu ncutangulo ampliato, siiprr- 

 ficie undique setosum ; semieellulis ellipticis vel subellipticis, divergentibus, dorso snliplariis, 

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

 subrectis. (R.) 



Z)iam.— 7125" = . 0017". 



Syn. — St. polytrichum, Perty. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 2l4. 



iZaft.— 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. 



Remarks. — This dcsmid appear-s to be rare in this coTintry, as it probably is also 

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

 near Clielten 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. Bavenelii, Wood. (sp. nov.) 



St. mediocre, paulo longius quam latum ; semieellulis a fronte ellipticis, a vertice triangularilnis 

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

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



Z>mm.— Long. „Vou'' = 0.0014". Lat. ^Vir" = 0-001". 



Hah. — 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. 



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

 plant ; fig. 22 a, the side view, and fig. 22 h, the end, all magnified 750 diameters. 



St. hirsutiini, (Eurb.) Breb. 



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

 sinu plus minus lineari, acutangulo; semieellulis late ellipticis vel subsemiorbicularibus, 

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

 rectis vel leniter convexis. (R.) Species mihi ignota. 



Dia„!._Sine spinis 0.0015". Zygospor. 0.0022". (R.) 



Sijn. — St. hirsutum, (Ehrenberg^ Br£bisson. Rabenhorst, Flora Europ. Algarum, Sect. 



III. p. 211. 

 finfc.—Florida; Rhode Island; Bailey. Rhode Island; (S. T. Olney) Thwaitcs. 



20 August, 1872. 



