Plate XXXVII ; Figures 238 to 244 ; Magnified 500 

 Diameters, except Figs. 243, 244. 



Fig. 238 



Fig. 239 



Fig. 240 



Fig. 241 



Fig. 242 



Fig- 243 



Fig. 244 



Micrasterias rotata (Grev.) Ralfs 



furcata (Ag.) Ralfs . 



Americana ( Ehrb. ) Kutz. 



m 11 ri cat a Bail. 



truncata (Corda) Ralfs 

 Coleochoeta scutata Iireb. 

 Cosmarium undulatum Corda (500 

 diameters) ..... 



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64 



