K II KSH-W ATKR A L G .V. OF THE UMTKD STATES. 153 



nts in f. T. triangular, ends truncate, rough with minute granules, tapering at each side 

 into elongate, straight, slender, lmri/.ontul processes, terminated by three or four minute 

 .--pino ; u. v. trirudiiite, processes utraight, sides concave. (A.) 



( I YTIOHEKMA 1'll.ciM M, M'lM LO8UM VEL ACULEATl M. 

 CVTIODEUM IMLOKK, 81'INfI.OSK OK THORNY. 



l. |>ol> lri limn l'i :., , 



St. mediocre, turn longum quani latum, profunde constrictum, 8inu acntangulo ampliato, super- 

 ficie undic|iie setosiini ; Kemicellulis elli|iticis vcl gubellipticis, divcrgcntilius, dorso subplanis, 

 M-iitre tumidis, margiiie setoso-ciliatis, a Tcrtice triaugularibus, augulis obtusis, lateribus 

 ubrectis. (II.) 



Diam. 7 i J" = .0017". 



$yn. St. polytrichum, PERTY. RABENIIORST, Flora Europ. Algarum, Sect III. p. 214. 



llab. Prope Philadelphia ; Wood. 



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

 widened, surface everywhere furnished with setae; 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 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 alga; 

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

 tion of Ilabenhorst, as given above. 



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



M. Ravenelii, WOOD. (sp. nov.) 



St. mediocre, paulo longins qnam latum ; semicellulis a fronte ellipticis, a vert ice triangularibu.s 

 urn lateribus convexis vel leniter retusis et angulis rotundatis ; i.-thmn connexivo subnullo, 

 lato ; sinu acutangulo ; cytiodcrmate epinis acuti.s, robustis numcrosis armato. 



Diam. Long. ^\ " = O.OOU". Lat. <" 0.001". 

 //,,/,._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 rctuse, and the angles rounded ; connecting isthmus 

 obsolete, broad sinus acute-angled ; cytiodcrm armed with numerous acute robust opines. 



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

 plant ; fig. 22 o, the side view, and fig. 22 t, the end, all magnified 750 diameters. 



*l. liirMiitimi, (EHRB.) BREB. 



St. magnum, tertiam partcm circitcr quam longins qnam latum, plus minus dense Rpinulosum, 

 sinu plus minus linear!, acutangulo ; semicellulis late cllipticis vel subsemiorbicnlaribns, 

 spinis tenuibns etrictis hirsutis, a vertice triangnlaribus, angulis obtuse rotnndatis, lateribus 

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



Diam. Sine spinis 0.0015". Zygospor. 0.0022". (R.) 



Syn. St. hirsutum, (EiiRENBERn) RREIIISSON. RABENIIORST, Flora Europ. Algarum, Sect 

 III. p. 211. 



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



20 August. 1873. 



