BRITISH UESMIDIEiE. 129 



Frond very minute, smooth, deeply constricted at the middle, the constric- 

 tion forming a linear notch on each side ; segments quadrilateral, twice as 

 broad as long, with one or two minute but stout teeth at each angle. End 

 view quadrangular, the sides concave, the angles truncate, and in British 

 specimens emarginate. 



A drawing of Stavrastnon qiiadrangulare sent me by Brebisson represents 

 a much larger form. Its angles, which in the end view are broader, have four 

 teeth at their truncate ends and two minute teeth on their upper surface ; but 

 I concur with Mr. Jenner in regarding the British plant as a small variety of 

 this species. 



Length of frond yyVr ^^ ^'^ "^^^^ 5 breadth -yywz '■> breadth at constriction 



2193' 



Tab. XXII. fig. 7. a. front view with endochrome ; b. empty frond ; e. end 

 view. 



Tab. XXXIV. fig. 11. a. front view from a drawing by M. de Brebisson ; 

 b. end view. 



15. S. sexcostatum (Breb.) ; segments in the front view with a toothed 

 angle at each side ; end view circular, with five or six broad, short, 

 toothed lobes. 



Staurastrum sexcostatum, Brebisson, Meneghini, Synopsis Besmid. in Linnaa 



1840, p. 228 ; Brebisson, in lit. cum icone. 

 Staurastrum Jenneri, Ralfs, Annals of Natural History, v. 15. p. 158. t. 11. 



f. 8 (1845) ; Transactions of Bot. Society of Edinburgh, v. 2. p. 144. 



t. 14. Jenner, Fl. of Tunbridge Wells, p. 194. 

 Goniocystis {Pentasterias) Jenneri, Hassall, Brit. Freshwater Algce, p. 356 



(1845). 



Very rare. Between Mayfield and Hadlow Down, Sussex, Mr. Jenner. 

 Yate near Bristol, Mr. Thwaites. Dolgelley, J. R. 



Falaise, Brebisson. 



Frond large, rough with conic granules which give a dentate appearance 

 to the outline ; segments about as broad as long, produced into a toothed angle 

 on each side, where also a triangular sinus is formed between the angles. The 

 end view is circular and elevated in the centre, and has five or six broad, short, 

 toothed, marginal lobes. The transverse view has a large central opening 

 surrovmded by a row of large granules. 



I refer this plant to Brebisson' s Staurastrum sexcostatum, on his own autho- 

 rity, but a dravdng sent by him of S. sexcostatum represents a smaller state. 



Length of frond -^^ of an inch ; breadth from ^-L to wr > hreadth at con- 

 striction y-gVy 



Tab. XXIII. fig. 5. a. front view of Sussex specimen ; b, c. end views ; 

 d. transverse \'iew ; e. front view of Dolgelley specimen. 



