152 FRESH-WATER ALG^E OF THE UNITED STATES. 



Syn. Var. St. cystocerum, BREBISSON. RABENHORST, Flora Europ. Algarum, Sect. III. p. 210. 



Hah. Rhode Island ; (S. T. Olney) Thwaites. 



Segments in f. v. subcuneate, 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 concave. L. -gJY'- !* E!I/'- (Archer.) 



St. p:i rodoMim. MEYEN. 



St. semicellulis inflatis, dorso rotundatis vel rectilinearibus, angulis superioribus in radium 

 elongatum achroum hispidum, apice trifurcatim productis, so:pius radio a-quali interposito 

 a vertice tri- vel quadriradiatis, radiis strictis, trifurcatis, longitudine corporis diam. a;quau- 

 tibus vel superantibus. (R.) 



Diam. Cum rad. .0015". 



Syn. St. parodoxum, MEYEN. RABENHORST, Flora Europ. Algarum, Sect. III. p. 210. 



Hab. 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 than 

 the diameter of the body. 



Remarlcs. 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 emuty frond. 



St. arachne, RALFS. 



St. parvum, gracile, granulato-asperum ; semicellulis introrsum ventricoso-globosis, angulis 

 superioribus in cornu gracile, incurvum, apice obtusum, elougatis, a vertice pentagonis, 

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

 (R.) 



Diam. Sine rad. .0005", cum rad. .00167". 



Syn. St. arachne, RALFS, British Desmidiese, p. 136. RABENHOBST, Flora Europ. Algarum, 

 Sect. III. p. 210. 



Hab. In lacu Saco, New Hampshire, (Lewis) Wood. 



Segments in f. v. stiborbicular, rougTi 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. 



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



St. gracile, RALFS. 



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

 valde inflatis, dorso truncatis, angulis in cornu rectum achroum gracile apice trifidum pro- 

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



Diam. 0.0022". (R.) 



Syn. St. gracile, RALFS, British Desmidiese, p. 136. RABENHOBST, Flora Europ. Algarum, 

 Sect. III. p. 211. 



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

 Thwaites. 



