298 



EUNOTIA. 



central nodule (which I had previously recorded in 1885 in my Synopsis), of 

 terminal nodules, and of a true raphe elevated on a keel, which he believes to 

 exist ; by the valves having a more delicate membrane, and by the frustules 

 being more or less asymmetrical. Mr. Otto Miiller includes in his genus 

 Rhopalodia, F.pithemia gi'bba, and its variety ventricosa, the very singular 

 species from Lake Nyassa, in Africa, which Dickie named Epithemia davata 

 in 1880, and lastly some new forms allied to the latter species which have their 

 habitat in the same region. 



Fig. 67. Eunotia gracilis. 



a Girdle view, 

 b Valve view. 



GENUS 36. EUNOTIA EHR, 

 1837. Char. Emend. 



Valve arcuate, without costae, trans- 

 versely striated, without raphe or central 

 nodule, furnished with pseudo nodules 

 at apices. Girdle face rectangular. 

 Frustules free or united in filaments 

 or parasitic on other plants. Endo- 

 chrome divided into two laminae on the 

 zone by a deep sulcus. 



I . Frustules united into filaments of greater or less length. 

 (HlMANTIDIUM AUCT.). 



Valves with ( 

 apices ' 

 capitate, 

 reflexed on 

 the dorsal 

 margin ; j 

 individuals 

 united in 



short 

 filaments. 



Valves with 



apices not 



capitate, 



straight or 



directed 

 towai ds the 

 ventral 

 I. margin. 



Frustules 

 large ; 

 striae 

 easily 



visible. 



Valves 

 rather 

 broad. 



Valve with apices sub-trun- 

 cate, strongly rostrate- 

 capitate . E. Arcus. 



Valve with apices obtuse- 

 rounded, scarcely capi- 

 tate . . E. major. 



Valves very narrow 



L Frustules very small ; striae scarcely visible 



. E. gracilis. 

 . E. exigua. 



Apices straight, produced, rostrate ; girdle face not 



showing imperfect divisions . . . E. pectinalis. 



Apices obtuse, not produced rostrate, directed towards 

 the ventral margin ; girdle face generally showing septa 

 arising from imperfect divisions , , . E. Faba 



