WISCONSIN PHYTOPLANETON 97 



var. EVOLUTUM W. & G. S. West. PL 76, Figs. 11-14. 

 Trans. Bot. Soc. Edinburgh 23: 25, pi. 2, fig. 31. 1905. 



Cells larger and with much longer and more delicate processes. 

 Vertical view triangular, with the sides slightly retuse and the angles 

 continued in straight processes with finely crenulate margins. Proc- 

 esses of one seraicell alternating with those of the other. (Faculta- 

 tive planktont.) 



Cells 40-51 fi long with processes, 23-25 ix long without processes ; 

 breadth with processes 51-63 /a, without processes 16-13 fi; breadth 

 at isthmus 4.5-6 ju,. 



Middle McKenzie (ss). 



var. TRiGONUM Lundell. PI. 76, Figs. 15-16. 



Nova Acta Eeg. Soc. Sci. Upsaliae 3 Ser., 8: 69, 1871; W. "West, Jour. Linn. 

 Soc. Bot. 29: 187. 1892. 



Cells small, fairly deeply constricted ; processes stout in proportion 

 to the size of the cells, divergent and with three or four deep crenu- 

 lations on both the upper and the lower margins, median portion of 

 processes with small spines. Vertical view triangular, with sides 

 slightly retuse and angles with stout straight processes, lateral mar- 

 gins of processes deeply crenulate and ends quadrispinate. (Tycho- 

 planktont.) 



Cells 32 ft long with processes, 22 /x long without processes ; breadth 

 with processes 42 [j. ; without processes 15 fj. ; breadth at isthmus 7 /x. 



Little Bass (rr), Crab (rrr), Horseshoe (rrr), Jones (rrr), Eed Bass (rrr), 

 Whitefish (rr). 



Lundell mentions triangular forms of S. tetracerum and William 

 West gives their dimensions. I have found a minute triradiate alga 

 which I believe to be the one described by Lundell. 



34. Staurastrum lacustre G. M. Smith. PL 76, Figs. 1-8. 



Trans. Wis. Acad. Sci., Arts & Lett. 20: 355, pi. 12, figs. 13-15. 1922. 



Cells of medium size, length (with processes) about equal to the 

 breadth, fairlj^ deeply constricted, sinus widely open and with apex 

 acute, isthmus fairly narrow; semicells obversely triangular, with 

 ventral margins straight or slightly tumid, dorsal margin flat, usually 

 with the median portion truncate and elevated; angles continued in 

 long slightly tapering processes that terminate in two very long di- 

 vergent spines, proximal portion of processes with upper and lower 

 surfaces coarsely crenulate and at times a median row of conical 

 granules, distal portion always smooth, processes always strongly 

 divergent; cell body without ornamentation except for two apical 

 emarginate verrucae. Vertical view triangular, sides straight or 

 slightly retuse; angles continued in long processes with subparallel 

 sides and terminating in two long spines that lie in the same ver- 



