GONIOCYSTIS. 353 



6. Trigonocystis ? aculeata Hass. 

 Plate LXXXIV. Fig. 12. 



Char. Fronds spinous. Segments in the front view, ^cith a 

 process on each side terminating in three minute spines. 

 End view triangular, with concave sides. 



yS End view quadrangular, with four distorted rays. 



Staurastrum aculeatum INIencgli., Synops. Desmid. p. 226.- 

 Dcsmidium aculeatum Ehr., Infiis. p. 142. t. 10. fig. 12. ; 

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

 clt. p. 194. 



Hah. Cross in Hand; Sussex, and Becklcy Furnace: 

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

 mon, Surrey, and Piltdown Common, Sussex: 3Ir. 

 Jenner. Penzance: 31?'. 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. Stjurastrvm Ehr. 



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

 segment diverging from those of the other. 

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



1. Staurastrum 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 quadrangidar. An- 

 gles obtuse, sides excavated. 

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



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

 therefore a Staurudnim ? 



A A 



