352 DESMIDE^. 



4. Trigonocystis hexaceros Hass. 

 Plate LXXXIV. Fig. 11. 



Char. Fronds rough. Segments ahovt twice as long as 

 broad, separated from each other by a deep notch, ttvisted. 

 End view triangular, icith concave sides and blunt entire 

 angles. 

 S. tricorne Meneghini, Synopsis Desmid, p. 225. Binatella 

 tricoryiis Breb., Alg. Fal. p. 57. (1835). Desmidium 

 hexaceros Ehr., Abhand. der Akademie d. Wisseusch. 

 zu Berlin (1832), p. 292. ; Ehr. Die Infus. p. 141. t. x. 

 fig. 10. Staurastrum tricorne Ealfs, in Annals, vol. v. 

 p. 155. pi. xi. fig. 2. ; Jenner, in loc. cit. p. 194. 

 Hab. Shallow pools, Piltdown Common; Ashdown Forest; 

 Rusthall Common ; between May field and Hadlow 

 Down: Mr. Jenner. Barmouth: Rev. T. Salivey. Dol- 

 gelly and Penzance : BIr. Ralfs. High Beech : A. H. H. 

 " The conic granules arranged in transverse lines at the 

 angles are generally very minute, but in some Sussex spe- 

 cimens gathered by INIr. Jenner they are large, and on the 

 margin produce a dentate appearance." — Ralfs. 



5. Trigonocystis gracilis Hass. 

 Plate LXXXV. Fig. 1. 



Char. Fronds muricated, deeply constricted in the centre, ttvo 

 or three times longer than broad, tapering on each side into 

 a slender process, ichich is terminated by three minute teeth. 

 End view triradiate. 

 Euastrum No. 13. ^ailey, in American Bacillaria, pi. i. 

 fig. 2 — 5. Staurastrum gracile Ralfs, in Annals, vol. 

 XV. pi. xi. fig. 3. 

 Hab. Boggy pools, Dolgelly, and Penzance : Mr. Ralfs. 

 Althougli but three processes or teeth usually present them- 

 selves to the observer, the real number is four ; but this is only 

 to be seen when one of the angles or rays is so situated that 

 its extremity is directly presented to the observer. 



