BY G. I. PLAYFAIR. 833 



Chodat. The cells are subcircular, arranged in a square, and 

 each furnished with a long, thin, delicate spine. Cytoplasm 

 pale green. 



Var. DENTATUM, u.var. (PI. Ivii., f.7,). 



Coenobium (4: cell.) (juadratum vel rhomboideum; lacuna dis- 

 Jbincta rectangulari; cellulis plus minusve ovatis adpi'essis, lateribus 

 angulatis, ad apices spinis longis tenuissimis singulis instructis et 

 altero latere dentibus vel spinis brevibus singulis. 



Coenob. (4 cell.) c. sj). diani. 30-38; cell, diani. 3-i/i. 



Pa r ram atta ( 1 3 6 ) . 



In this form, the cells are more or less ovate, with angular 

 sides, adpressed, the apices outwards, and furnished with a long, 

 thin spine. A little lower down, on one side, is a second, much 

 smaller spine or tooth. The lacuna is sharply rectangular. 



Genus C CE L A s T R u M Nag 



C'a7. niicrupuruDi Nag., is by far the most connnon form in 

 this country, and, next to it, Cml. creuatiuu Arch. C. sphteri- 

 cnni Nag., very rare. 



CtELASTRUM CRENATUM Archer. 



Ccenob. diam. 32-83; cell. diam. 6-32/x. 

 Collector, Rose's Lagoon; Botany (91); Guildford (124). 

 Cy: G. 8. West, Brit. Frw. Alg., p. 2 13, f.87A. Syn., Ccel. 

 pufchrum 8chm., Algentl. d. Schwarzw. u. d. Rheineb., T. ii., f. 10. 



Var. CUBICUM, n.var. (Pi. Ivii., f.8). 



Ciienobium plus minusve uubicum angulis truncatis; cellulis 

 quattuor circa unum ordinatis; foraminibus amplis octagonis. 



Caniob. diam. 33-55; cell. diam. c. 10/x. 



Guildford (77). 



Generally the cells are arranged 5 or (i round (ine, in this form 

 4, which gives the ccenobium a cubical or octagonal shape; the 

 foramina, also, are wide and octagonal in outline. Very like 

 C. cjihicuni, but that species has three projections to each cell, 

 two visible at the margin. 



