832 AUSTRALIAN f"RESHWATER PLANKTON, 



Crucigenia cordata, nom.nov. 



C'(LMi()b. in medio furaniine parvo rectangulari instructum ; 

 cellulis plus minusve cordiforniibus, uti;iiique ad apices apiculo 

 mimito interdum ornatis. 



Ccenob. (4 cell.) long. 25, lat. 23/z, 



Botanic Gardens (158). 



.Syn., Pedi. tetr-as \a,r. inteyrum (Nag.) Playf., forma. I.e., p.518, 

 P1.56, f.7. The cells are more or less heart-shaped, and are often 

 tipped with a minute, indistinct apiculus. The species should 

 be compared with Fedi. tetras var. ajnctdatnm, supra. 



Crucigenia triangularis Chodat. (PI. Ivii., f.4). 



Coenob. diani. 10-16; cell. diam. ca; 5-7/x. 



Collector; Guildford (88); Lismore (188). 



C/. Chodat, Alg. vertes, p. 223, f. 14-1 9. The ccenobium con- 

 sists nearly always of 4, minute, pale green, ovate cells, occa- 

 sionally with pyrenoids. 



Crucigenia quadrata var. secta, n.var. (PI. Ivii., f.5). 



Cellulfe circulatJB in partes subtriangulares 4 per crucem 

 divisse. 



Crenob. (4 cell.) long. 6, lat. 6; cell. diam. ca. 2//.. 



Lismore (188). Cum. C. rectamjnlari. 



The original ccenobium, before division, must have been con- 

 stituted of 4 circular cells arranged in a square; hence, I have 

 placed this form under C. quadrnta Morren, cf. G. S. West, Brit. 

 Frw. Alg., p. 2 16, f.90D, e. Pale green in coloui-. 



Genus T e t r a s t k u M Chodat. 

 Tetrastrum elegans, n.sp. (PI. Ivii., f.6). 

 Ccenobium (4 cell.) quadratum; cellulis subcirculatis distinctis, 

 extrorsum spinis longis tenuissimis singulis ornatis. 

 Ccenob. diam. c. sp. 28, cell. diam. 4/x. 

 Parramatta (136). 



This species might be described as a spinous form of C. 

 quadrata Morren, just as T. stauroyenio'forme of C. triangularis 



