620 SOME SYDNEY DESMIDS, 



Xan. octonarium Nord. var. cornutum, n.var. (Plate xii., fig 7). 



Forma dimidio longius diametro (sine cornibus). Semicellulse 

 regulariter subreniformes, tres quadrantes circuli efficientes, 

 apicibus planis; lateribus cornibus geminatis 3 munitis, cornibus 

 rectis, conicis, validis, acuminatis, radiantibus. A vertice semi- 

 cellulse latissime ellipticse vel ovales, apicibus late-rotundatis. 

 Membrana achroa, glabra, subtiliter punctata, nullo tumore nee 

 incrassatione. TJnara tantum cellulam vidi. 



Long. c. corn. 96, s. corn. 84; lat. c. coin. 84, s. corn. 58; crass. 40: 

 long. corn, ad 15/z. 



Botany. 



This is probably a young form of Xan. octonarium Nord. I 

 have it from Botany, whence all my specimens of that species 

 have come. The number of spines is very irregular, vide my 

 notes in these Proceedings, 1907, p. 178, where a specimen with 

 six spines on one side and seven on the other is given as 

 82 x 58 x 37/a, agreeing very well with that here figured. The 

 characteristics of var. cornutum are the stout conical aculei, and 

 the absence of the central incrassation. 



Xan. gloriosum G S. West, in Hardy, Frw. Alg. of Victoria, 

 Vict. Nat. xxiii. p. 19. 



Xan. pvlcherrimum Playf., I.e. p 180, according to a figure 

 kindly supplied by Mr. Hardy. 



Xan. simplicius Nord., Frw. Alg. N.Z. T.4, f.26. 



Long. c.ac. 36, s.ac. 24; lat. c.ac. 30, s.ac 24; lat. isth. 6; long. 

 ac. 4-5/i. 



Botany (2). 



Var. Botanicum niihi (X. Botanicum Playf., I.e. p. 182). 

 (Plate xi., fig.10). 



Figura I.e. data non typica. Semicellulse lateribus valde retusis, 

 apicibus etiam atque ad basin plus minus parallelis. Angulis 

 in aculeos productis, superioribus leviter incurvis, basalibus 

 patentibus. 



