GONIOCYSTIS. 355 



Hah, Dolgelly and Penzance : Mr. Ralfs. 



This Staurastrum is to be distinguished from the previous 

 species by the trifid extremities of the rays. 



4. Staurastrum ? bifidum Ralfs, 



Plate LXXXV. Fig. 2. 



Char, Frond smooth, hut little constricted in the centre, truncate 

 laterally. Rays trijid. End view triradiate. 



Desmidium hifidum Ehr., Die Infus. p. 141. t. 10. f. 11.; 

 Ralfs, 1. c. p. 151. pi. X. fig. 3. 



Hah. Dolgelly and Penzance: Mr. Ralfs. 



The smoothness of the frond will always distinguish this 

 from the previous species. It should probably be referred to 

 Trigonocystis, 



Section iii. Pentasterias Ehr. 



Char. Frond in front view without diverging processes. End 

 view circular, with usually five rays. 



Derivation. From ir£VT£,five, and aa-TSpia^, starred. 



1. Pentasterias arachnis Hass. 



Plate LXXXV. Fig. 8. 



Char. Frond rough, deeply constricted in the centre. Seg- 

 ments ahout as long as hroad, suhorhicular, with elongated 

 slender hyaline and incurved processes. End view Jive- 

 rayed. 



Staurastrum Arachne Ralfs, in Annals, vol. xv. p. 157. 

 pi. xi. fig. 6. 



Hah. Boggy pool near Dolgelly, very rare : Mr. Ralfs. 



" This plant is remarkable for its slender processes which 

 will easily distinguish it from ♦S'^. margaritaceum. It cannot 

 be a five-rayed variety of St, gracile, for the rays are longer, 

 more slender, remarkably incurved, and also entire at the 

 extremity." — Ralfs. 



A A 2 



