20 



B. Individua in fascias conjuncla. 



62. Pleurostaurum 



(acutum). 



Stauroneis in fascias con- 

 juncta. 



63. Diadesmis:* 



(confervacea). W 



: : 



*[* MP f« )« 



WMZrfcrty* 



Frustula navicularia, in fascias 

 conjuncta. 



t . Intlividnu in massa gclatinosa nidiilantia. 



a) in aqua dulci, nonnunquam extra aquam. 



64. Frustulia: 



(saxonica). 



Frustula navicularia , linea 

 media medio interrupta, 

 nodulo centrali nullo. 



a o 



65. Mastogloia : H^ | h 



(Danscii). 



jl Frustulanaviculacea mucomatri- 

 r cali mammaeformi involuta. 



66. Colletonema: 



(viridulum). 



Frustula naviculacea 

 tubo gelineo in- 

 clusa. 



