138 BRITISH DESMIDIEjE. 



Ehreuberg and Meneghini unite the Micrasterias tetracera of Kutziug to 

 the Staurastrum paradoocum, Meyen ; but whilst the latter plant has four 

 processes at each end, this has only two, which, if I am correct in my \'iew of 

 the following species, differ also by ha\dng entire extremities. 



Length of frond 21^03 ^^ ^^ mch. ; length of process -j yVo '■> breadth of 

 frond YT&T- 



Tab. XXIII. fig. 7. a, b, c. front views ; d. empty frond ; e. frond with one 

 segment not fully developed ; /. end view. 



29. S. paradoxum (Meyen) ; frond rough ; front view with elongated 

 diverging processes which are minutely trifid at the apex ; end view 

 quadrangular or sometimes triangular. 



/S. End view triradiate. 



Staurastrum paradoxum, Meyen, Nov. Act. Leop. Holm. v. 14. p. 43. f. 37, 



38 (1828). Meneghini, Synop. Desmid. in Linncea 1840, p. 227. 



Ralfs, Jnnals of Nat. Hist. v. 15. p. 151. t. 10. f. 2; Trans, of Bot. 



Soc. of Edinhin-gh, v. 2. p. 137. t. 13. 

 Micrasterias Staurastrum, Kiitzing, Synop. Diatom, in Limusa 1833, 



p. 599. 

 Phycastrum paradoxum, Kiitzing, Phycologia Germanica, p. 138 (1845). 

 Goniocystis (^Staurastrum) paradoxum. Hassall, Bi'it. Freshwater Alg. p. 354 



(1845). 



Dolgelley and Penzance, J. R. Near Bristol, 3Ir. Thioaites and Mr. 

 Broo7ne. Ambleside, Mr. Sidebotham. Banffshire and Aberdeensliire, Mr. 

 P. Grant. Near Pulborough, Cross-in-Hand, &c., Sussex, Mr. Jenner. 



Germany, Meyen, Kutzing. Falaise, Brebisson. West Pouit, New York, 

 Bailey. 



Frond very minute, generally much constricted at the middle, the ends 

 truncate ; each segment has, generally, four elongated processes diverging 

 from those of the other segment. The end ^aew is sometimes triradiate, but 

 usually quadriradiate ; I have also seen specimens in which one segment had 

 four and the other only three rays. In the front view, as the frond generally 

 rests on one side, each segment appears to have only two processes, the other two 

 being covered by them ; but sometimes only one process is thus hidden, and 

 occasionally all four may be seen at the same time. The processes are elon- 

 gated, colourless, and, being rough with minute granules arranged in transverse 

 lines, have a jointed appearance ; each terminates in three minute spines. In 

 the newly-formed segment the processes are mere conical projections. 



Wlien only two processes are seen at each end, in the front view, this spe- 

 cies is very like the preceding ; but its frond is more constricted, larger and 

 of a deeper green, and its processes are thicker and not entire at the apex. 



Length of frond ^^ of an inch ; breadth jxbt J breadth at constriction 

 J J^3 ; length of process from Y3V2 to yy'y^. 



Tub. XXIII. fig. 8. a, b, c. front views of mature fronds; d, e. end 

 views ; f. immatuic frond. 



