STREPTOTHECA. 



463 



GENUS 129. STREPTOTHECA CLEVE, 1890. 





7 O C??rfc> 



ft/ 





'ooo 



o o o 



Or? 



OoOO 





OO^C>o C 





00 c 



pet 







O 



0OQ 



Fig. 194. Streptotheca Tamesis. 



Frustules not silicious, forming a long flat ribbon, twisted on itself 

 at regular intervals. One species : 



