ARTHRODESMUS. 357 



1. Artiirodesmus convergens Ehr. 



Plate LXXXV. Fig. 9. 



Cha7\ Segments broader than lonrj, somewhat elliptic, elon- 

 gated at each side into an incurved spine. End view 

 compressed, with a spine at each extremity. 



Artiirodesmus convergcns Ehr., Iiifus. p. 152. t. 10. fig. 18. 

 Staurastrum convergcns INIenegli., Synops. Desmid. 

 p. 228. ; Ralfs, in Annals, vol. xv. p. 158. pi. xii. fig. 1. ; 

 Bailey, Amer. Bacil. pi. i. fig. 11. ; Jenner, in loc. cit. 

 p. 194. 



Hah. Brarabletye, near East Grinstcad ; Rackliam Com- 

 mon, near Pulborough, Sussex ; and Rustliall Common, 

 near Tunbridge Wells : Mr. Jenner. Dolgelly and 

 Penzance : 71/?-. Balfs. Cliesliunt : A. H. H. 



The incurA^ed mucroncs will at once serve to distinguish 

 this species. 



2. Arthrodesmus Incus Hass. 

 Plate LXXXV. Fig. 10. 



Char. Segments externally lunate, xcith a mucro at each 

 angle. End A'iew elliptic, mucronatcd at each extremity. 

 Euastrum Bailey, Amer. Bacil. pi. i. fig. 12. ? Staurastrum 

 Incus Meneghini, Synops. Desmid. p. 228. ; Balfs, in 

 Annals, vol. xv. p. 159. pi. xii. fig. 2. ; Jenner, p. 194. 



Hah. Weston Bogs, near Southampton ; Rackham Com- 

 mon, near Pulborough, Sussex : Mr. Jenner. Dolgelly 

 and Penzance : Mr. Balfs. 



The mucro in tins species is turned outwards : in the front 

 view the segments resemble those of Trigoyiocystis mucrO' 

 nata, but the end view is very diftcrent. 



3. Artiirodes.aius octocornis Ehr. 



Plate LXXXV. Fig. 11. 



Cliar. Fronds compressed. Segments broader than long, 

 A A V, 



