99 



S t a u r a s t r LI m a r m i g e r u m Bréb. Zygosp . globular, with nu - 

 merous spines, which are broad at the base und taper to a fine, 

 slightly bifid apex. Diam., exclusive of sp., 41 y..; length of sp., 12 a. 

 (T. Ili, f. 12). 



S. pseu dofu rcige r um Reinsch , « Acta Semckenb. » 18Ò7 und 

 «Die Algenflora» 1867, ist, den Vcrf. nach, synonym mit S. armi- 

 gerum Bréb. 



S. dilata tum Ehr. Somewhat barrel-sliaped, with round ends, 

 and has numerous raised bands, passing longitudinally roud it, giving 

 the end view an undulated appearance. Diam. 48 a. (T. IV, f. 4). 



S. furcigerum Bréb. Zygosp. exactly like that of S. armige- 

 rum in size and appearance. 



S. granulosum Kg. Zygosp. globular, with numerous slightly 

 bifid spines. Diam. without sp., 28 y.; length of sp., io u.. (T. Ili, f. ó). 



S. paradoxum Mey. Globular, not large, with few long spines, 

 2-3 -fid at the apex. 



S, pileolatum Bréb. Pretty large, globular, with not very nu- 

 merous stout spines, 2-3-fid at the apex. 



S. scabrum Bréb. Globular, sometimes slightly oblong, with 

 short stout spines, 3-4-fid at the apex. About loto i3 visible round 

 the margin. Diam. without sp., 32-35 y..; length of sp., 5-6 y.. 



Arthrodesmus octocornis Ehr. Globose, or ovoid, with 

 long, slender, tapering, acute, simple spines. — /3 m aj r Ralfs. Si- 

 milar to the common form, only larger and with longer spines. Diam. 

 without sp., 2Ó y.; length of sp , 20 y.. (T. II, f. 20). 



Die Zygoten der Hauptform sind schon frùher beschrieben worden. 



C s m a r i u m a n g u 1 s u m Bréb. Zyg. globose-octahedral, with 

 eight subacute undulations round the margin. 



C. cor bui a Bréb. Globose, with about ni ne rather slender, 

 slightly trifurcate spines round the margin (T. II, f. 18). 



C. tetrachondrum Lund. Small, smooth, and globular, some- 

 times showing a tendency to elongate irregularly. 



Closterium arcuatum Bréb. Globular, 27-29 y.. in diam.; 

 conjugating fronds crossed. 



C. Ceratium Perty. Zygosp. small, smooth, orbicular, placed 

 betwen the conjugating fronds; very like to that of C. gracile Bréb. 



C. gracile Bréb. Zygosp. thick walled, yellowish, globular; bet- 

 ween the conjugating fronds; diam. 22 '/,, y. 



Die Zygoten dieser Art sind schon frùher beschrieben. 



C. interni ed ium Ralfs Thickwalled, yellowish, globular; con- 



