AETHRODESMUS. 357 



1. Artiirodesmus convergens Ehr. 



Plate LXXXV. Fig. 9. 



Char, Segments broader than long, somewhat elliptic, elon- 

 gated at each side into an incurved spine. End vie^\ 

 compressed, with a spine at each extremity. 



Arthrodesmns convergens Ehr.^ Infus. p. 152. t. 10. fig. 18. 

 Staiirastrum convergens Menegh., Synops. Desmid 

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

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

 p. 19-1. 



Hah. Brambletye, near East Grinstead ; Backham Com- 

 mon, near Pnlborough, Sussex ; and Bustliall Common, 

 near Tunb ridge Wells : Mr. Jenner. Dolgelly and 

 Penzance : Mr. Ralfs. Clieshunt : A. H. H. 



The incurved mucrones will at once serve to distinguish 

 this species. 



2. Arthrodesmus Incus Hass. 



Plate LXXXy. Fig. 10. 



Cliar, Segments externally lunate, ivith a mucro at each 

 angle. End view elliptic, mucronated 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; Backham Com- 

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

 and Penzance : Mr. Ralfs. 



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

 view the segments resemble those of Trigonocystis mucrO' 

 nata, but the end view is very different. 



3. Arthrodesmus octocornis Ehr. 



Plate LXXXY. Fig. 11. 



Char. Fronds compressed. Segments broader than long, 



A A 3 



