GONIOCYSTIS. 353 



6. TKIGONOCYSTIS ? ACULEATA Hass. 

 Plate LXXXIV. Fig. 12. 



Char. Fronds spinous. Segments in the front view, with a 

 process on each side terminating in three minute spines. 

 End view triangular ', with concave sides. 

 f3 End view quadrangular, with four distorted rays. 



Staurastrum aculeatum Menegh., Synops. Desmid. p. 226. 

 Desmidium aculeatum Ehr., Infus. p. 142. t. 10. fig. 12. ; 

 Ralfs, in Annals, vol. xv. pi. xi. fig. 4. ; Jenner, in loc. 

 cit. p. 194. 



Hob. Cross in Hand ; Sussex, and Beckley Furnace : 

 Mr. Jenner. Penzance : Mr. Ralfs. /3. Woking Com- 

 mon, Surrey, and Piltdown Common, Sussex : Mr. 

 Jenner. Penzance: Mr, Ralfs. 



The spines are larger and longer in this than in any other 

 species of the genus. The variety, which I have not seen, 

 would appear to be referrible to the species proper, and is 

 therefore very interesting.* 



Section ii. STAURASTRUM Ehr. 



Char. End view quadrangular, often four-rayed, rays of one 

 segment diverging from those of the other. 



Derivation. From aravpos, a cross, and aeTpov, a star. 



1. STAURASTKUM DILATATUM Ehr. 

 Plate LXXXV. Fig. 5. 



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

 ments twice as broad as long, obtuse at the sides, and not 

 elongated into processes. End view quadrangular. An- 

 gles obtuse, sides excavated. 



Ehr. Die Infus. p. 143. t. 10. fig. 13. ; Menegh. Synops. 



* Is not the normal number of rays in this species four, and is it not 

 therefore a Staurastrum ? 



A A 



