24 WISCONS-IN PHYTOPLANT 70N 



protuberances just above the smaller ones of the inferior row. Ver- 

 tical view elliptic, with poles rounded and four protuberances on each 

 side. Lateral view oblong-pyramidate, with basal portion subquadrate 

 and sides converging to a quadrate apex, angles somewhat rounded. 

 Chloroplast with a central axial plate from which radiate four parietal 

 plates, two to each cell face; pyrenoids 5-8, all in parietal plates. 

 ( Tychoplanktont. ) 



Zygospores unknown. 



Cells 104-110 IX long ; 58-61 fi broad at basal lobes of semicells, 

 40-42.5 ju, at median lobes, 28-31 /a at apical lobe, 17.5 /u. at isthmus; 

 apical incisions 5-7 [i deep. 



Little Doctor (rrr), Lost (rrr). 



Differing from E. didelta in the deeper incisions forming the lobes 

 and in both number and arrangement of the protuberances on the 

 cell wall. 



5. EuASTRUM piNNATUM Ralfs. PI. 56, Fig. 5. 



Brit. Desm. 81, pi. 13, figs. lA-lE. 1848; W. & G. S. West, Monogr. Brit. Desm. 

 2: 10, pi. 34, figs. 3-6. 1905. 



Cells fairly large, length about twice the breadth, deeply con- 

 stricted, sinus narrowly V-shaped to linear, with apex expanded, 

 isthmus narrow; semicells truncate-pyramidate, distinctly five-lobed, 

 polar lobe anvil-shaped, with apex concave, angles broadly rounded 

 and polar incision deep and expandesl towards the apex; incisions 

 forming l«bes deep but widely open and with rounded apices ; superior 

 lateral lobes elongate-mamillate, with superior margin at right angles 

 to inferior margin and forming an angle of 45 degrees with the long 

 axis of the semicell; inferior lateral lobes subquadrate, with margins 

 strongly retuse and angles rounded. Cell wall punctate, with a large 

 protuberance just above the isthmus and one within each lateral lobe 

 as well as with two smaller protuberances at bases of lateral lobular 

 incisions. Vertical view elliptic, with poles mamillate and each side 

 with three protuberances. Lateral view of semicells narrowly 

 truncate-pyramidate, with lateral margins concave just below the 

 apex and angles rounded. (Tychoplanktont.) 



Zygospores unknown. 



Cells 137.5 ix long ; 67 [x broad at basal lobes of semicells, 57 fx broad 

 at median lobes, 35 /<, at apical lobes, 19 /a at isthmus; apical incision 

 6.5 ju, deep. 



Crooked (rrr), Found (rrr). 



6. EuASTRUM Glaziovu B0rgesen. PI. &6, Fig. 6. 



Vidensk. Medd. f. d. naturhist. Forening i Kiobenhavn 1890: 36, pi. 3, fig. 23. 

 1890. 



Cells somewhat under medium size, length about twice the breadth, 

 very deeply constricted, sinus linear, with apex somewhat inflated 

 and outer margin widely open, isthmus very narrow; semicells dis- 

 tinctly three-lobed, polar lobe almost anvil-shaped, with angles some- 

 what rounded and each bearing a stout horizontally disposed spine. 



