PLATE LXVI. 



FIGS. PAGE 



13. Cosmarium venustum, Breb. 1 and 2, x 520; 



3, x 400 . . . ' .8 



4. C. venustum forma minor Wille. x 400 . 10 



5-6. C. venustum var. liypoliexagonnm West, x 400 10 

 7-8. C. Garrolense Roy & Biss. 7, x 600 (after 



Roy & Bissett) ; 8, x 520 . .12 



9-10. C. Eeinscliii Arch. 9, x about 750 (after 

 Reinsch) ; 10, form with rounded apical angles, 

 x 520 . . . .12 



11. C. EeinsMi var. eboracense West & G. S. West. 



x 500 . . . . 13 



12. C. Nagelianum Breb. x 600 (after Nageli) . 14 

 13-14. C. orthogonum Delp. x 416 (after Delponte) . 118 

 15-16. C. notabile Breb. 15 3 x 500; 16, zygospore, 



x 520 . . . .15 



17. C. notabile forma minor Wille. x 400 (after 



Wille) . . . .16 



17A. C. anceps Lund, forma crispula Nordst. x 400 49 

 18-19. C. notabile forma media Gutw. 18, x about 



500 (after Gutwinski) ; 19, x 660 . . 17 



20-21. C. tetragonum Nag. a and a, x 600; c, x 300 



(after Nageli); 21, x 400 . . 17 



22. C. tetragonum var. heterocrenatum West & G. S. 



West, x 520. . . .19 



23-24. C. tetragonum var. LnndeUiiCodke. 23, x 500; 



24, x 400 (after Lmidell) . .18 



25-26. C. tetragonum var. Davidsonii (Roy & Biss.) 

 West & G. S. West. 25, x 600 (after Roy 

 & Bissett) ; 26, x 500 . . 20 



27. C. tetragonum var. elegaris (Roy & Biss.) West 



& G. S. West. x 400 (after Roy & Bissett) 20 



