182 SOME NEW OR LESS KNOWN DESMIDS FOUND IN N. S. WALES, 



of the apical ones, are curved in towards the apex of the cell. 

 This large number of teeth, greater even than in X. octonarium, and 

 their entirely different shape, seem to me to distinguish this 

 species from all forms of X. fasciculatum. The specimen was 

 surrounded by a gelatinous sheath 200/n in diameter. Cf. also 

 X. superbum Elf v. forma Borge, in Bail., Bot. Bull, xv., T.14, f.l. 



Xan. Botanicum, n.sp. (T.iv. f.l 3). 



Xan. minimum, oblongum, tam latum quam longum, medio 

 sinu cuneato profundissime constrictum, isthmo angustissimo. 

 Semicellulae subhexagonae, lateribus brevibus levissime retusis. 

 apicibus latis truncatis, angulis in aculeos singulos longos. infe- 

 rioribus horizontaliter, superioribus radiatim, productis; in centro 

 tumore rotundato conico ornatae. A vertice ellipticae utroque 

 latere tumore parvo conico instructae apicibus acuminatis in 

 aculeos singulos protractis. Membrana subtiliter punctata. 



Long. c.ac. 40; long. s.ac. 27; long. ac. ad. 12 : lat. c.ac. 43; lat. 

 s.ac. 24; lat. isth. 6 : crass. 12/i. 



Botany. 



The nearest forms to this seem to be X. simplicius Xord., Alg. 

 N. Z. T.4, f.2t), and Ar. octocornis Ehr., cf. Cooke, Brit. Desm. 

 T.47, f.2; also Ar. longispinus Borge, Desm. Braz. T.3, f.35, which 

 has no tumour, and X. controversum var. pla7ictonicum West, 

 Scott. Plankt. T.16, f.2-3, which is twice the size, with the tumour 

 scrobiculate. 



Genus Staurastrum Meyen. 



St. forcipatum, n.sp. (T.v. f.l). 



St. parvum, subcirculare, ad latera profunde excavatum, sinu 

 nullo, isthmo angustissimo, paullo latius quam longura. Semi- 

 cellulae subellipticae, dorso convexo, depress© ; angulis lateralibus 

 subacutis in aculeos breves singulos productis, aculeis assurgenti- 

 bus; a vertice triangulares, lateribus concavis, angulis acutis 

 leviter inflatis, aculeis singulis munitis. Meml^rana glabra. 



Long. 32; lat. 39; lat. isth. 8fi. 



Botany. 



