528 PLANKTON OF THE SYDNEY WATER-SUPPLY, 



Syn., Cylindrocystis miniitissimaTurn., Alg. E. Ind., Pl.i., f.24. 



In some specimens, the suture was evident. 



P. 2ioJymo7'ph^ltn Perty, is very common round Sydney, and 

 there is not the slightest doubt that the three foregoing are grow- 

 ing forms of it. They are all frequent in the filter samples, and 

 associated also in Sydney gatherings. Cf. also Schmidle, Alg. 

 Schwarz. u.d. Rheinbene, p. 21, T.iii., f.8-11. 



Genus Cosmarium Corda. 



Cos. CAPiTULUM var. DKTRITUM, n.var. (PI. liv., f.l2). 



Forma apicibus lateribusque perfeete levigatis, angulis superi- 

 oribus non productis. 

 Long. 16; lat. 20 /x. 



Cos. CONTRACTUM var. ELLIPSOIDEUM f. INTERMEDIA, n.f. 



Forma var. ellipsoideo consimilis sed circa dimidio minor. 

 Long. 20 30, lat. 15-24; isth. 3-5 /x. 



F. MINOR Rac. 



Long. 12-18; lat. 9-14; isth. 3 4 /x. 



The size of Cos. contrachim var. ellipsoideuTn is 48-51 x 

 38-42. All sizes occasionally have an incrassate spot in the 

 centre of the semicell, a characteristic which they owe to their 

 being young forms of Xati. hastiferum, etc. Connected with 

 them in the same life-history, are Cos. suhtumidum Nord., 

 Cos. phaseolus y achondrum Boldt, and Cos. foveatum Schra. 



Cos. ellipsoid e mil , type, is the same as Cos. incrassatum 

 Playf., an4ea, 1907, PI. v., f.l5, but without the incrassate 

 spot. 



Var. suBFOVEATUM, n.var. (PI. liv., f.l3). 



Semicellulae subreniformes, apicibus levissime truncatis ; 

 sinu extrorsum aperto ; angulis lateralibus latissime-rotunda- 

 tis ; lateribus arcuatis ad apices convergentibus. Membrana 

 punctata, tractu incra.ssato vel macula infra apices instructa. 

 Pyrenoidibus singulis. 



Long. 33-46; lat. 26-38; isth. 6 /x. 



