BY G. I. PLAYFAIR. 535 



Cf. Polyedrium pentagonum Reinsch, Algenfl. v. Frank., T.iii., 

 fig. ii.c( = Tetr. caudatum Corda) which is exactly the same shape 

 but without the two niamniillate angles which jut out from one 

 side. 



Tetraedron regulare v. octaedricum (Rein.) mihi. 



Cellulse angulis senis octonisve praeditae. (PI. Ivii., f.23). 



Cell. diam. 1 7/x. Lismore. 



Cf. Polyedrium octaedricum v. spinosum Reinsch, Algenfl. v. 

 Frank., p. 78, T. v., fig. v., 1867. In this place, Reinsch has 

 united two distinct types under onename"^ {P. octaedricum Rein., 

 Monog. Polyedr., p. 507, 1888). The first of these. T. v., fig. iv., 

 must retain the specific name, while the other, T. v., fig. v., is 

 evidently a form of I'etr. regulare Kiitz. ( = P, tetra'edricum Nag.), 

 with from six to eight angles instead of four. Our specimens 

 are the same shape as Reinsch's fig. v. 6, but very much smaller; 

 he gives lat. 38-47/x. 



Tetraedrox hastatum v. elegaxs Playf. 

 Cell. diam. c. proc. 30/x. Noted lately at Lismore (362), only 

 known previously from Parramatta. Cf. Austral. Frw. Phytopl., 

 p.845, PI. Iviii., f.27. 



Tetraedron acutum v. rectilineare Playf. 

 Cell. diam. c. spin. 34-40/x, sp. long. 1 0/x. Confirmed from 

 Lismore (362), only recorded previously from Enoggera; ibidem, 

 p.8-45, PI. Iviii., f.26. 



Tetraedron conicum, n.sp. (}'l. Ivii., f.24). 



Celkdjc tetraedricai; angulis conicis vix inflatis; apicibus mu- 

 ticis, obtuse-rotundatis; lateribus levissime conciivis. 



Cell. diam. 19-25//,. Lismore (362). 



The cells are tetrahedral, composed of four conical* angles 

 meeting in the centre. The angles can hardly be called inflated, 

 the sides of the cones being almost straight. The apices are 

 bluntly rounded, without point or spine. 



" Polyedrium acuminatum spino8iun at the bottom of Plate v., I.e., is 

 either a slip of tlie pen or a priiiter'.s error. 



