Plate XXY ; Figures 166 to 171 ; Figs. 168, 169 Magnified 

 500 Diameters ; all others iooo Diameters. 



Fig. 166. Closterium Letbleinii Kiitz. . . page 61 

 Fig. 167. var. curt 11 in West " 



Fig. 168. rostratum Ehrb. 



Fig. 169. var. 



breviro stratum West 

 Fig. 170. Closterium subcostatum Nord. With 



only 6 costae ..... 

 Fig. 171. Closterium Brebissonii Delp. . 



11 a 



