Joiirn.Q.M.C. 



Ser. 2.VolXIII,Pl,28. 



11 



12 



13 



14. 



5 g 





15. 



16 



^^ ^ 



@' 



17. 



18 



19. 



lel.N.Yermoloff. 



Adlard &. Son & West. Newman Ltd.litli. 



Variation in the genera Navicula-Cymbella. 



