530 PLANKTON OF THE SYDNEY WATER-SUPPLY, 



152 /A in diameter. This mucous investment is a sure sign that 

 the cell has been under conditions of partial dessication ; it 

 is not the sign of a sporangial form. ('. alpestre is a form of 

 C. tu7'gidum produced by repeated mitosis. Cf. also C. turgidum 

 var. subrotundafuni West, in W. &, G. S. West, Monog. iii., Pi. 75, 

 f.4. C. subturyidiim(Ty\vn.) Schm., I.e., PL 74, f. 22-23, is also a 

 form of C. turyidum. 



Cos. BiNUM var. fontense (Playf.). (PI. liv., f.l7). 



Semicellulae longitiidine latiores, levissirae truncatae; crenis 

 circa 20, saepe emarginatis. Infra marginem granulis gemi- 

 natis in seriebus 3 et granulis singulis in serie unica ordinatis 

 ornatae. Ad isthmum tumore grannlis magnis 5 et supra 

 jugis verticalibus 5 instructo. Circa tumorem area nuda. 



Long.56-64; lat.45-50; crass.30-34; i.sth.l5; apexl5/x. No.22. 



Syn., ('ox. suhnperiosum fSvalidius forma fontensls Playf. 

 ly(i)ite(t 1907, p. 198). As the tumor seems to be characteristic 

 of Goa. binum Nord., I have arranged the above under that 

 form. In the shape of the semicells, however, it agrees with 

 Co.'f. .<!iib.<ipeciosiiTn (i vrdidivs Nord. It is very near to Cos. 

 bxnum var. australiensis Borge, Austral. Siisswasserchlor, T.iii., 

 f.42. 



Genus Staurastrum Meyen. 



St. connatum var. muticum, n.var. (PI. liv., f.l8). 



Forma var. Spencerl(tno consimilis sed sine spinis. 

 Long. 20; lat. 18-21; isth. 4/i. 



The same form, with short spines, was common in most of 

 the samples. 



St. margaritaceum var. cruciatum, n.var. (PI. liv., f.l9). 



Semicellulae a fronte campanulatae, parte superiore in pro. 

 cessus producta ; apicibus levigatis, leniter arcuatis ; basis 

 granulorum minutorum seriebus singulis ornatis. A vertice 

 4-radiatae, processibtis latis cuneatis, granulorum seriebus 

 ternis transver.sis ornatis ; apicibus 4-fidis granulatis, non- 



