356 DESMIDEJE. 



2. PENTASTERIAS MARGARITACEA Elu. 

 Plate LXXXV. Fig 7. 



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

 tenuated at their junction, with short lateral converging 

 processes which are entire at their apices. End view with 

 Jive, rarely sip or seven, short obtuse rays. 



Staurastrum margaritaceum Menegh., Synops. Desmid. 

 p. 227. ; Ralfs, in Annals, vx>l. xv. p. 157. pi. xi. fig. 7. 

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

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



Hob. Dolgelly : 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 Jive, sometimes six, broad short-toothed rays. 



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

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



Hob. 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- 

 pressed, angles prolonged into a spine. 



Derivation. From apffpov, a joint, and Seoy/,oy, a link. 



The stout spines terminating the angles of the segments 

 seein to connect this genus with Xanthidium. 



