WISCONSIN PHYTOPLANKTON 



93 



Fig. 10. Staurastrum vestitum Ealfs (x600). 

 Lewis, Scotland, by W. & G. S. West. 



Specimens collected at Tarbert, 



intramarginal row of four verrucae on each side, the two central ver- 

 rucae arcuate and tridenticulate, the two terminal verrucae of each 

 row broad and emarginate. (Tychoplanktont.) 



Zygospores spherical, clothed with elongate processes with inflated 

 bases and bifurcate apices (Wolle). 



Cells 40 ju, long ; breadth with processes 58 fx, without processes 25 ju, ; 

 breadth at isthmus 10 /a. 



Found (rrr), Lost (rrr). 



The few examples seen in Wisconsin lakes have a much more abrupt 

 transition from the body of the semicells to the processes (as seen in 

 vertical view) than is ordinarily the case. Since our specimens are not 

 quite typical a figure is given of an English plankton specimen. 



The determination of this species is an easy matter when the cells 

 are viewed from above, the long verrucae projecting at right angles 

 from the cell immediately separating it from the other species. 



var. suBANATiNUM W. & G. S. West. PI. 75, Figs. 6-10. 

 Trans. E07. Irish Acad. 32: 54, pi. 1, fig. 28. 1902. 



Cells with smaller bodies but longer and less robust processes ; length 

 of processes greater than the diameter of the cells; ornamentation as 

 in the type but with the verrucae smaller and the terminal spines of 

 the processes larger; processes slightly divergent. Chloroplast axial, 

 with the central mass small and with a broad deeply furcate lobe run- 

 ning to each angle of the cell; pyrenoid single and central. (Euplank- 

 tont.) 



Cells 30-42 /x long with processes, 22-30 /x long without processes ; 

 breadth with processes 70-81 /x, without processes 23-32 /x ; breadth at 

 isthmus 10.5-11.5 fi. 



Diamond (sss), Jag (rr), Eed Bass (rrr). 



This variety is very happily named since it bears a striking resem- 

 blance to some of the pelagic varieties of S. anutinum Cooke & Wills. 



