24 EXPLANATION OF THE PLATES. 



Fig. 11. Gyrosigma Hippocampa : a, front view ; b, side 

 view. Fig. 12. Nitzschia elongata: a, front view; b, side 

 view. Fig. 13. Navicula inequalis. Fig. 14. Navicula 

 lanceolata. Fig. 15. Surirella Jenneri: a } front view; 

 by end view. Fig. 16. Navicula. 



PLATE CIIL 



Figs. 1 and 2. Zygnema insigne. Fig. 3. Coccochloris cysti- 

 fera. Fig. 4. Coccochloris variabilis. Fig. 5. Coccochloris 

 obscura. 



