\ 





- : 





'II 



. 











- 









m 



~4- 





mm 



Fig. 133. Rhizosolenia styliformis. 



GENUS 84.-RHIZOSO- 



LENIA (Ehr. Brightw.) 



Perag. era., 1892. 



Frustules subcylindricai, 

 very elongated, silicious, con- 

 sisting of numerous joints 

 with an annulate or imbricate 

 arrangement ; valves asym- 

 metrical, generally termina- 

 ting in a hood (calyptra) sur- 

 mounted by a bristle (seta) or 

 mucro. 



About 40 species in this 

 genus have been described, 

 but only some 30 deserve 

 attention. Seven inhabit the 

 North Sea. 



