50 A Canadian Arctic Expedition, 191S-18 



Plate IV. 



Fig. 1. Cosmarium Cucumis Ralfs, X 500. 



Fig. 2. " Subcucumis Sohmidle, X 500. 



Fig. 3. " punctulatum Brfib. var. subpunctulatum (Nordst.) Borg. 



Fig. 4. " trachypleurum Lund. var. minus, Raoib., X 500. 



Fig. 5. " subtumidum Nordst. var. Klebsii W. and G. S. West, X 500. 



Fig. 6. " binum Nordst. forma, X 500. 



Fig. 7. " globosum Bulnh., X 500. 



Fig. 8. " SiauTostnim Eeinschii Roy, X 500. 



Pig. 9. " /arafferam Br6b. An abnormal form with an extra unpaired process (x). 



Fig. 10. " vestitum Ralfs, X 500. c' normal, c" variation with additional process. 



Fig. 11. " lunatum Ralfs. 



Pig. i2. " Bribissonii Archer, small spines at angles, X 500. 



Fig. 13. " Avicula Brfeb., X 500. 



Fig. 14. " pachyrhynchum Nordst., X 500. 



Fig. 15. Oedogonium nodulosum Wittr., X 300. 



Fig. 16. Closterium Comu Ehrenb., showing variation in size and shape, all X 500. 



Pig. 17. Nephrocytium obesum W. West, X 500. 



Fig. 18. Gomphosphaeria aponina KUtz., X 500. 



a, face view; b, side view; c, end view. 



