fey a. I. PLAYFAIR. 845 



more or less concave sides, angles very acute and produced. The 

 angles are furnished with fine spines; it is sometimes difficult to 

 say where the angle ends and the spine begins. 



Var. RECTILINEARE, n.var. (PI. Iviii., f.26). 



Cellula; tetraedricfe; lateribus planis nee retusis; angulis acutis 

 haud protractis, spinis singulis prieditis. Cell. diam. c. sp. 25//.. 



Enoggera. 



The cell is tetrahedral; in optical section, triangular, with sides 

 quite flat, angles acute, not produced, furnished with short spines. 

 Nageli's figure, Gatt. einz. Alg., T. iv,B, fig. lb, is a plane form of 

 this variation. 



Tetk. hastatum var. eleoans, n.var. (PI. Iviii., f.27). 



Cellulfe tetraedricje; lateribus concavis; angulis in processus 

 hyalinos bifidos singulos protractis. Cell. diam. c. proc. 32/t. 



Parramatta Park (136). 



Cf. 7W)'. {Polyedrium) hastalitm Reinsch, Algenfl. v. Frank., 

 p. 77, T. v., f.3, also Chodat, I.e., p. 172, f.95. The sides of the 

 cell are very concave, and the single process at each angle more 

 regular; the processes are hyaline, and bifid, with recurved ends, 

 sometimes doubly dichotomous. 



Tetr. trigonum var. mammillatum, n.var. (PL Iviii., f. 28). 



Cellulte planfe triangulares; lateribus convexis; angulis obtusis 

 in papillas singulas productis; a latere viste lenticulares. 



Cell. diam. 12/x. Lismore (258). 



Cf. Tetr. (^Polyedrium) triyouum var. crassum Nag., in Eichler, 

 Flor. wodor. ok. Miedzyrzeca, 1892, T. ix., f. 17. This form has 

 each angle produced into a short, mammillate projection. 



Tetraedron cruciporme, n.sp. (PL Iviii., f.29). 



Cellulse planae, angulis radiantibus 4 exstructse, medio valde 

 constrictse, inferne et superne retusa:;; angulis acutis vix inflatis, 

 spinis minutis singulis instructis, Chloroplastides dilute virides. 



Cell. long. c. sp. 18, centr. 10; lat. c. sp. 20, constr. 6/x. 



Botany. 



A plane form, deeply constricted in the middle after the style 



