WISCONSIN PHYTOPLANKTON 83 



Vertical view triangular (rarely quadrangular), with sides retuse 

 and the angles continued in broad processes, processes of one semi- 

 cell usually alternating with those of the other. Ceil wall smooth and 

 without ornamentation. Chloroplast axial, with two lobes running 

 to the end of each process; pyrenoid single and central. Cells fre- 

 quently imbedded in a copious spherical gelatinous envelope with a 

 radially fibrillar structure. (Facultative planktont.) 



Zygospores pentahedral to octohedral, with sides straight; angles 

 rectangular and continued in blunt spines (Ralfs, Eichler) or angles 

 rounded and spines scarcely visible (W. & G. S. West). 



Cells 28-35 jx long with processes, 15-17.5 p. long without processes; 

 breadth with processes 27.5-34 /x ; breadth at isthmus 8-9 ju,. 



Carroll (rrr), Dummy (s), Little Bass (rrr). 



G. S. West has discussed the variation of this species and states 

 that the processes may be long and somewhat tapering or short and 

 blunt. The apices may be either bi- or trifurcate and with the fur- 

 cations ranging from a rather long incision (usually in the individuals 

 with bifurcate processes) to small rounded knobs that show but little 

 furcation. 



23. Staurastrum pseudopelagicum W. & G. S. West. PI. 72, 



Figs. 5-7. 



Jour, Linn. Soc. Bot. 35: 547, pi. 18, figs. 1-3. 1903; Trans. Eoy. Soc. Edin- 

 burgh 41: 504. 1905. 



Cells fairly small, length (without processes) about twice the 

 breadth, deeply constricted, sinus widely open to acute-angled and 

 with an acuminate apex, isthmus narrow; semicells obversely semi- 

 circular to subtriangular, with apices flattened to convex; angles of 

 semicells prolonged into long divergent processes that have their apices 

 terminating in two or three long outwardly curved and divergent 

 spines ; subapical portion of processes with concentric rings of gran- 

 ules, basal portion with scattered granules; apex of semicells smooth 

 or irregularly granulate. Vertical view triangular, with sides con- 

 cave to convex and with the angles continued in long processes that 

 terminate in three to two spines, when bispinate with the spines in 

 the same vertical plane ; body of the cell smooth to granulate ; 

 processes ornamented as in the front view. (Euplanktont.) 



Zygospores unknown. 



Cells 40-55 p. long with processes, 24-30 p long without processes ; 

 breadth with processes 54-71 fx, without processes 18-31 p.; breadth at 

 isthmus 6.5-8.5 p. ; length of terminal spines 5-8 p.. 



Devils (rrr). Shell (sss). 



The figures which W. & G. S. West give of the alga have a stouter 

 cell body than is shown in my drawing. The more delicate form that 

 I have figured is almost identical with a form of S. psuedopelagicum 

 in the plankton from Loch Morar, Scotland, in the G. S. West coUec- 



