842 AUSTRALIAN FRESHWATER PLANKTON, 



tainly a form of Tetr. minhmim, being commonly found in com- 

 pany with other forms of the species. 



Var. PINACIDIUM (Reinsch) mihi. (PI. Iviii., f.l4, 15). 



Cell. long. 6-13, lat. 5-1 1/x. 



Botanic Gardens (3); Clyde, Duck Creek (26); Botany (108). 



Polyedrium pinacidium Reinsch, Spec, generibusque, T.2a, 

 f. iii.; Lagex'heim, Pedi. Protococc. o. Palm., p.69, T. i., f.27. Syn., 

 P. Tninimum f. tetralohula Reinsch, Polyedr. Monog., T. iv., fig. 2d 

 (forma tetralohulata in text, p.499); P. tPtrayonum Reinsch (non 

 Nag.), I.e., T. iv., f. 10. The cell is plane, with rounded angles, 

 all four sides equally retuse. Reinsch and Lagerheim figure the 

 cell as quadrate; our specimens were somewhat oblong. 



Var. RECTILINEARE, n.var. (PI. Iviii., f. 16, 17). 



Cellulae plus minusve quadratae, lateribus rectilinearibus, 

 angulis obtusis plus minusve rectis. 



Cell. long. = lat. = 10-1 3/x. Guildford. 



Cells more or less regularly square, with flat sides and bluntly 

 rounded angles. Cf. Bernard, Protococc. et Desm., f.467. 



Var. MORSUM (W. & G. S. West) mihi. (PL Iviii., f.l8). 



Cell. long. = lat. = 9/i,, constr. 8/x. 



Botanic Gardens (3). 



I'etrapedia morsa W. & G. S. West, Frw. Alg. Madag., p.85, 

 PI. v., f.3. The sides of the angles are flattened, and run back 

 at right angles from the apex, for about one-third the length of 

 the side of the cell. The other third is occupied by a sudden, 

 rounded excavation. Cell plane, contents green; found in com- 

 pany with var. pinacidmyn and the type, very rare. 



Tetraedron regulare Kiitz., forma. (PI. Iviii., f.l9). 



Cell. diam. c. sp. 34, s. sp. 24)u. Parramatta (136). 



Kiitzing, Phycolog. germ., p. 129. Syn., Polyedrium teira- 

 edricum Nag., pro parte, Gatt. einz. Alg., T. iv.B, fig.3c, d. P. 

 trigonuni Nag., 2}.p., loc. cit., T.iv.B, fig.lc, d. I am in great 

 doubt as to the characteristics of this type. Both Chodat, Alg. 

 vertes, p.220, f.146, and G. S. West, Brit. Frw. Alg., p. 231, f.lOlc, 



