BY G. I. PLAYFAIR. 331 



Var. MAMMILLATUM Playf. (Pl.xlii., f.ll6.) 



Long, semic. 20, lat. 40, isth. 6, ap. 28, basis 25 /x. 



Lismore(240). 



Cf. Some Sydney Desm., p 619, PI. xii., f.6. 



Var. CKACOViENSE(Rac. ) mihi. (Pl.xlii., f.96, 10.) 



Forma semicellulis Cos. pseudoprotuber^anti similibus, latioribus 

 autem; sinu lineari, aut angusto introrsum ampliato; angulis 

 superioribus magis subapicalibus. 



Long. 36-44, lat. 32-44, basis 20-24, isth. 8 fi. 



Lismore (240). Cum prioris duabus. 



Syn., Cos. contractum var. Cracoviense Rac, Desm. Polon., p. 28, 

 T. X., f.lO. Found also as a mixed form with X. inchoatum, f., 

 supra. However much this may resemble Cos. pseudoprotuberans 

 it is quite certainly a spineless form of X. inchoatnm, produced, 

 as were the forms with it, by repeated self-division. We are 

 here faced by a serious difficulty in the nomenclature, viz., what 

 to do with these pseudo-Cosmarm, a large number of which are 

 included in the genus Cosmarium, but are, biologically, forms of 

 Xanthidium, and can be found Sisformce mixtce with semicells of 

 that genus. 



Var. ALPiNUM (Rac.) mihi. (Pl.xlii., f.lla.) 



Long, semicell. 18, lat. 38, basis 25, isth. 6 fx. 



Lismore (240). Cum precedentibus quattuor. 



Syn., Cos. pseudoprotubera7is var. alpinum Rac, Desm. Polon., 

 p.27, T. x., f.ll. The latter is very much smaller (long. = lat. = 

 10'5-12'5, isth. 6-5 fx, Rac), but agreeing so exactly in shape with 

 our form that I thought it best to accept the name. The equality 

 of length and breadth also is characteristic of Xan. inchoatum 

 and its forms. 



Genus S t a u r a s t r u m Meyen. 

 St. tonsum (Nord.) mihi. 

 Long. 46-54, lat. 70-88, bas. inll. 18-20, isth. 11 /x. 

 Lismore (185). 



Syn., St. pseudosebaldi* tonsum Nord., Frw. Alg. N.Z., p. 36, 

 T.4, f.4. The form agrees almost exactly with the lower 

 semicell of JSordstedt's specimen. Others with more slender 



