WISCONSIN PHYTOPLANKTON 95 



The primary distinction of the variety is the great length of the 

 processes, the length being greater than the breadth of the body of 

 the semicells. It also differs from the type in that the processes are 

 less divergent and have concentric rings of grannies at the base. The 

 breadth with processes of the Wisconsin specimens is not as great as 

 that of specimens from Scotland. 



var. cuRTUM G. M. Smith. PI. 75, Figs. 17-20. 

 Trans. Wis. Acad. Sci., Arts & Lett. 20: 354, pi. 12, figs. 6-7. 1922. 



Cells smaller, semicells broadly cyathiform and with apex flattened, 

 processes short and only subdivergent, cell body without the subapical 

 row of verrucae. (Euplanktont.) 



Cells 35-48 /x long with processes, 25-28 jx long without processes ; 

 breadth with processes 55-74 /x, without processes 24-33 jt^; breadth 

 at isthmus 9-11 jx. 



Bass (rrr), Beaverdam (rrr), Cranberry (rr), Crawling Stone (rr), Found 

 (rrr), Hill (r), Horseshoe (rrr), Lac Court Oreilles (rrr), Lindy (ss). Long 

 (rrr), Jones (rrr), Nicaboyne (rrr), Sand (rrr). 



The variety is distinguished from another small variety (pelagicum 

 W. & G. S. West), found in British lakes, by the different proportions 

 between length and breadth of the semicells, smaller degree of diver- 

 gence of the processes, cell size, and the lack of the subapical verrucae. 

 The cell shape and ornamentation is quite similar to the variety 

 longihrachiatum but the processes are very much shorter. 



var. denticulatum var. nov. PI. 75, Figs. 21-25. 



Shape of the semicells as in the variety curium; processes with very 

 long denticulations on the upper and the lower margins; cell apex 

 with small straight linear verrucae and small linear subapical ver- 

 rucae. (Euplanktont.) 



Cells 36-50 /a long with processes, 26-34 /x, long without processes ; 

 breadth with processes 60-86^1; without processes 26-34 /i; breadth 

 at isthmus 10.5-12 ju,. 



Carroll (sss), Jag (rr). Mud (sss), Sishebogema (rrr), Tied Canoe (rrr). 



The variety is distinguished by the great development of the teeth 

 that ornament the processes and the reduction in size of the apical 

 and subapical verrucae of the body of the cell. These smaller ver- 

 rucae have the same position as those of the type but are not nearly 

 so conspicuous, especially in a vertical view. In one case they were 

 not regularly arranged but were scattered coarse granules (Fig. 21). 



The spiny nature of the processes is quite similar to that of an 

 alga from the plankton of Canadian lakes that I have considered a 

 variety (verrucosum) of S. aspinosum Wolle. The relative length 

 of the processes and the breadth of the cell body as well as the orna- 

 mentation of the cell body are quite distinct in the two algae. 



