356 DESMIDE.E. 



2. Pentasteeias maegaritacea Ehr. 



Plate LXXXV. Fig 7. 



Char. Frond rough. Segments in front view siibglohose, at- 

 tenuated at their junction, with short lateral converging 

 l^rocesses which are entire at their ajjices. End view ivith 

 Jive, rarely six or seve?i, short obtuse rags. 



Staurastrum margaritaceum Menegli., Synops. Desmid. 



p. 227. ; Ralfs, in Annals, vol. xv. p. 157. pi. xi. fig. 7. 



Pentasterias margaritacea Ehr., Infus. p. 144. t. 10. 



fig. 15. ; Jenner, in loc. cit. p. 194. 

 Hah. Dolgellj : Mr. Ralfs. Ashdown Forest, Sussex : 



Mr. Jenner. 



The rays are much stouter and shorter in this than in the 

 preceding species. 



3. Pentasterias Jenneri Hass. 



Plate LXXXV. Fig. 6. 



Char. Fronds large, dentated. Segments about as broad as 

 long, lengthened into a toothed angle on each side. End 

 view with five, sometimes six, broad short-toothed rays. 



Staurastrum Jenneri Palfs, in Annals, vol. xv. p. 158. 

 pi. xi. fig. 8. ; Jenner, in loc. cit. 



Hab. Mayfield, Sussex : Mr^ Jenner. 



A very fine species. " The transverse view has a large 

 central opening surrounded by a row of large granules." — 

 Ralfs. 



55. ARTHRODESMUS Ehr. 



Char. Fronds smooth, deeply constricted. End view com- 

 jjressed, angles prolonged into a spine. 



Derivation. From apOpov, a joint, and heajjios, a link. 



The stout spines terminating the angles of the segments 

 seem to connect this genus with Xanthidium. 



