152 FRESH-WATER ALGJ3 OF THE UNITED STATES. 



S>/n.— Vat: St. ci/docerum, Beebisson. Rabenhorst, Flora Europ. Algarum, Sect. HI. p. 210. 



2fa6.— Rhode Island ; (S. T. Olncy) Thwaites. 



Segments in f. v. subciineate, gradually widening upwards, truncate at the end margin, rough 

 with minute granules, the lateral processes incurved, divided at the apex ; e. v. triradiate, 

 processes short, curved, sides slightly coucave. L. ^Ju". B. jj-j". (Archer.) 



St. parodoxum, Meyen. 



St. seniicelluli.s inflatis, dorso rotundatis vel rcctilinearibus, angulis supcrioribus in radium 

 elongatum achroum hispidum, apiee trifurcatim productis, sajpius radio aujuali interposito 

 a yertice tri- vel quadriradiatis, radiis strictis, trif'urcatis, longitudine corporis diani. a^quau- 

 tibus vel superantibus. (R.) 



Diam.— Cum rad. .0015". 



Syn.—Sf. parodoxum, Meyen. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 210. 



Jlab. — In lacu Saco, New Hampshire ; (Lewis) Wood. 



Semicells inflated, dorsum rounded or rectilinear, with superior angles produced into elongate, 

 transparent, hispid radii with trifurcate apices, often furnished also with intermediate equal 

 radii ; from the vertex three or four radiate, radii straight, trifurcate, equalling or longer thau 

 the diameter of the body. 



Remarks. — I am indebted to Dr. Lewis for specimens of this species, which he 

 collected at Saco Lake. 



Fig. 20, pi. 21, represents the end view of an empty frond. 



St. arachne, Ralfs. 



St, parvum, graeile, granulato-asperum ; semicellulis introrsum vcntricoso-globosis, angulis 

 supcrioribus in cornu graeile, ineurvum, apiee obtusura, elongatis, a vertice pentagouis, 

 qui.nque-radiatis, radiis elongatis linearibus achrois, obtusis, rectis vel leniter curvatis asperis. 

 (RO 



i)/am.— Sine rad. .0005", cum rad. .0016r'. 



Syn. — St. arachne, Ralfs, British Desmidica;, p. 13G. Rabenhorst, Flora Europ. Algarum, 

 Sect. III. p. 210. 



Hah. — In lacu Saco, New Hampshire, (Lewis) Wood. 



Segments in f. v. suborbicular, rough with minute granules, lower margin turgid, outer convex, 

 tapering at each side into an elongate, slender, incurved process having the granules thereon 

 in transverse lines, entire at the apex; e. v. circular, bordered by five slender, linear, colorless 

 marginal rays. 



Remarh. — Fig. 21, pi. 21, represents an outline of the end view of the semicell. 



St. graeile, Ralfs. 



St. mediocre, granulate asperum, granulis in series transversas ordinatis ; semicellulis ventre 

 valde inflatis, dorso truncatis, angulis in cornu rectum achroum graeile apiee trifidum pro- 

 ductis, a vertice triradiatis, lateribus sinuatis. (R.) Species mihi ignota. 



Biam.— 0.0022". (R.) 



Srjn. — St. graeile, Ralfs, British Desmidicoe, p. 13G. Rabenhorst, Flora Europ. Algarum, 

 Sect. III. p. 2n. 



Zfrtft.— South Carolina; Florida; Georgia; Rhode Island; Bailey. Rhode Island; (Olney) 

 Thwaites. 



