14 



38. Grammonema: 



uv 



39. Raphoneis: 



(a. et b. Rhombus ; 

 c. niediterranea). 



40. Doryphora = Rhaphoneis stipitata. 



Frustula quadrangula , a 

 fronte (a. b. c.) lanceolata 

 (a), elliptica (b) vel late 

 elliptica et utroque polo 

 late rotundata (c), nodulo 

 centrali destituta , striis 

 vel costis transversis, ubi 

 adsunt, medio vitta vel 

 area longitudinali inter- 

 ruptis. 



41. Synedra: 



(Ulna). 



Frustula fronte (a) lineari-lanceolata, 

 striis transversis parallelis linea longi- 

 tudinali medio interruptis , nodulo 

 centrali annuliformi ; latere lineari- 

 rectangula , striis marginalibus ab- 

 breviatis, nodulo centrali nullo. 



