78 WISCONSIN PHYTOPLANKTON 



17. Staurastrum quadrangulare De Brebisson forma. PI. 70, 



Figs. 8-9. 



in Ralfs, Brit. Desm. 128, pi. 22, figs. 7A-7C; pi. 34, figs. IIA-IIB. 1848; 

 W. & G. S. West, Trans. Linn. Soc. 2nd. Ser. Bot. 5: 257, pi. 16, figs. 16-17. 

 1896; Borge, Arkiv for Botanik 1: 108, pi. 4, fig. 17. 1903. 



Cells small, length about equal to the breadth, median constriction 

 fairly deep, sinus subrectangular and with a blunt apex; semicells 

 rectangular, with apex and lateral margins straight, lateral margin 

 with a short curved spine at the superior and inferior angles, spines 

 outwardly divergent; apex with a short perpendicular spine just 

 within each lateral margin. Vertical view quadrangular, with 

 strongly retuse sides and flattened emarginate corners each bearing 

 two curved spines, basal portion of the semicell extending beyond 

 the truncate angle, rounded, and with a single straight spine. (Tycho- 

 planktont.) 



Zygospores unknown. 



Cells 27.5 ju, long with spines, 22 fi long without spines ; breadth with 

 spines 25 fi, without spines 20 fi ; breadth isthmus 10 [x. 



Lindy (rrr). 



But two cells of this alga have been seen and although they un- 

 doubtedly belong to the species they do not agree precisely with any 

 published figures. 



18. Staurastrum breviaculeatum sp. nov. PI. 70, Figs. 10-18. 



Cells small, length and breadth about equal, deeply constricted, 

 sinus acute-angled and with apex subacuminate, isthmus narrow; 

 semicells transversely elliptic, dorsal margin sometimes flattened in 

 the median portion ; lateral angles broadly rounded and bearing four 

 short quadrately arranged divergent spines ; cell body with two trans- 

 verse rows of 4-7 spines, the lower row half way between the isthmus 

 and the cell apex, the upper midway between the lower row and the 

 apex; cell apex with median portion bare and with margins towards 

 the angles with 3-4 outwardly pointing spines. Vertical view tri- 

 angular, sides of cells emarginate and angles broadly rounded and 

 bearing four quadrately arranged short divergent spines; center of 

 cell body with a triangular ring of spines, the sides of the triangle 

 lying parallel to the margins of the cell and each side composed of 

 three outwardly facing spines, angles of the central triangle con- 

 nected to the corresponding angle of the cell by a short row of spines ; 

 lateral margins of cells with 6-8 erect spines and a second arcuate 

 intramarginal row of spines that are of similar size and arrangement ; 

 outline of cell slightly emarginate between adjacent spines. Chloro- 

 plast with a small central mass and two laminate blades running to 

 each angle of the cell; pyrenoid single and central. (Euplanktont.) 



Zygospores unknown. 



Cells 38-46 /t long with spines, 36-42 fi long without spines ; breadth 

 with spines 37-55 fx, without spines 34-44 /x ; isthmus 9-13 /* broad ; 

 spines 2-5 /i long. 



Bass (rrr), Devila (rrr), Speese (rrr), Sunday (rrr). Tank (rrr), Travis (r). 



