84 WISCONSIN PHYTOPLANKTON 



tion. Since no form name was given to this I have not named the 

 Wisconsin form. The original description states that the processes 

 are terminated by two large divergent spines but in the local collec- 

 tions trispinate specimens are more abundant than bispinate. This 

 point is of no taxonomic significance since both may occur on different 

 processes of the same semicell. Although W. & G. S. West make no 

 mention of the fact, the same variation occurs sparingly in the speci- 

 mens from Loch Morar. 



The distinguishing features of the species are the shape of the semi- 

 cells, the nature of the sinus, the granulation of the cell wall, and the 

 terminal spines of the processes. It should be compared with 

 S. pelagicum W. & G. S. West, with S, lacustre G. M. Smith, and 

 with certain forms of S. paradoxum Meyen (especially those figured 

 by W. & G. S. West, Jour. Linn. Soc. Bot. 35: 548, pi 18, fig. 5. 

 1903). 



var. tumidimi var. nov. PI. 72, Figs. 8-11. 



Sinus always acute-angled; divergence of the processes not so 

 marked and the transition from the body of the cell to the processes 

 more gradual, ends of processes generally with three straight diver- 

 gent fairly long spines, rarely with two or four spines ; concentric 

 granulation of processes much more pronounced than in the type ; 

 curvature of the apex of the semicells much greater and with one or 

 two short spines near the point of origin of each process. Vertical 

 view triangular, body of the cell granular to smooth. (Euplank- 

 tont.) 



Cells 40-55 fx long with processes, 24-31 /x long without processes ; 

 breadth with processes 54-80 /a, without processes 19-25 ju,; breadth 

 at isthmus 6.5-8 fx ; length of terminal spines 5-7 /x. 



Devils (rrr), Grindstone (sss), Lae Court Oreilles (ss), Lae du Flambeau (rrr), 

 Whitefish (ss). 



The variety differs from the type in the greater curvature of the 

 cell apex, different shape of the sinus, and greater regularity of 

 granulation. The terminal spines are conspicuous, as in the type, 

 but are straight, not curved, and more variable in number. 



24. Staurastrum cingulum (W. & G. S. West) G. M. Smith. PI. 72, 



Figs. 12-14. 



Trans. Wis. Acad. Sci. Arts & Lett. 20: 353. 1922. 



Staurastrum paradoxum var. cingulum W. & G. S. "West, Jour. Linn. Soc. Bot. 

 35: 548, pi. 18, figs. 6-7. 1903. 



Cells of medium size, length (without processes) about one and 

 three quarters that of the breadth, slightly constricted, sinus a small 

 subrectangular depression, isthmus broad ; semicells subcylindrical, 

 without a basal inflation and with a ring of 12-15 minute spines (7-9 



