GONIOCYSTIS. 353 



6. Trigonocystis ? aculeata Hass. 

 Plate LXXXIV. Fig. 12. 



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

 process on each side terminating in three minute spines. 

 End view triangular, with concave sides, 

 (3 End view quadrangular, with four distorted rags. 



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 loo. 

 cit. p. 194. 



Hab, Cross in Hand ; Snssex, and Beckley Furnace : 

 Mr, Jenner, Penzance : Mr. Ralfs, — j3. 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 varietg, which I have not seen, 

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

 therefore very interesting.* t 



Section ii. Staurastrum Ehr. 



Char. End view quadrangular, often four-raged, rags of one 

 segment diverging from those of the other. 



Derivation. From cnavpos, a cross, and aarpov, a star, 



1. Staurastrum dilatatum Ehr, 



Plate LXXXV. Fig. 5. 



Cluir. Frond rough, deeplg constricted in the centre, Seo"- 

 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 Stmanstrum ? 





dV A 



