212 WISCONSIN PHYTOPLANKTON 



var. cuRVATUM W. & G. S. West. PL 80, Figs. 11-14. 

 Jour. Linn. Soc. Bot. 35: 549, pi. 18, fig. 9. 1903. 



Cells somewhat larger than the type, less deeply constricted ; semi- 

 cells obversely subtriangular and with apices bearing small truncate 

 verrucae ; processes outwardly divergent. Vertical view four- or 

 five-radiate, with central area of cell smooth or with a truncate ver- 

 ruca midway between each pair of adjacent processes. Chloroplast 

 axial, with a small central body and a lobe arising midway between 

 bases of processes, lobes with laminate ends, a single lobe running 

 into the base of adjacent processes; pyrenoid single and central. 

 (Euplanktont.) 



Cells 36-40 fx long with processes, 18-25 /n long without processes ; 

 breadth with processes 62-74 fx, without processes 18-20 ju. breadth at 

 isthmus 8.5 jn. 



Carson (rr). Crab (sss), Dummy (rr), Dutchmans (rrr), Jag (rr), Lae Court 

 Oreilles (rr). Shell (rrr). 



The chief feature of the variety is the outward curving of the 

 processes in the front view of a cell. There is also a difference in 

 the ornamentation of the top of the cell and the cell shape. In the 

 Wisconsin plankton the four-radiate specimens predominate. 



48 Staurastrum pentacerum (Wolle) G. M. Smith. PI. 80, 



Figs. 15-18. 



Trans. Wis. Acad. Sci., Arts & Lett. 20: 356, pi. 12, figs. 19-22. 1922. 



Staurastrum Ophiura var. pentacerum Wolle, Bull. Torr. Bot. CI. 9: 28, pi. 13, 

 fig. 5. 1992; Desm. U. S. 134, pi. 43, fig. 13; pi. 44, fig. 3. 1884. 



Cells of medium size, length about one and a half times the breadth 

 (without processes), slightly constricted, sinus a small semicircular 

 indentation, isthmus broad; semicells trapeziform-quadrate, with the 

 apex slightly tumid and broader than the base, body of the semicell 

 without ornamentation and apex with a row of subapical verrucae, 

 processes arising just below the apex, subparallel, somewhat attenu- 

 ated and terminating in three short divergent spines, dorsal margin 

 finely crenulate, ventral margin smooth. Vertical view five-radiate 

 (rarely six-radiate), with the processes of one semicell alternating 

 with those of the other semicell ; body of cell pentagonal or hexagonal, 

 with sides retuse, and with a single broad emarginate verruca be- 

 tween each pair of processes, at times with two smaller verrucae one 

 on each side of this larger verruca, central area without ornamenta- 

 tion; processes slightly tapering and with lateral margins crenulate 

 or with two rows of spines. Choloroplast axial, massive, with reni- 

 form lobes arising between the bases of adjacent processes and with 

 a single plate-like process running a short distance into each ad- 

 jacent process. (Facultative planktont.) 



Zygospores unknown. 



Cells 36-41 /A long ; breadth with processes 85-105 jii, without proc- 

 esses 18-20 ja ; breadth at isthmus 10 jx. 



