STAURASTRUM. 1 53 



Differs from the type in the possession of an apical 

 ring of about 9 or 10 verrucae. which are visible as 

 emarginate granules across the apex in the front view. 



Length 37 JJL ; breadth, without processes, 15-20 y. ; 

 breadth, including processes, 55-71 tj. : length of pro- 

 cesses 20-27 [JL ; breadth of isthmus 9 JJL. 



IRELAND.- -Lough Alachugh, Donegal ! In lakes, Clif- 



vden to Roundstone, Ualwav ! 



</ 



146. Staurastrum Ophiura Lund. 

 (PL CLII, figs. 1. 2.) 



Staurastrum <J/i/iii/r<i Lund. Desin. Suoc. 1^71. p. ti'.i. t. 4. t. 7: Xordst. 

 Norgea l)->m. IS73, p. 3.1 : \V.II>, Dosm. I". S. lss4. p. 134. t. 43, f. 10, 

 11 : Cookp, Brit. Desni. 1SS7, p. 172 (<h^<-r. only): DC T.uii. Syll. Alg. 

 INS!*, p. 1212; \\Vst \- (J. S. \\Vst. Some X. Am.-r. D.-sm. 1896, p. 208, 

 t. IS. f. Hi; Sc,,tt. Fivshw. Plankton. I. 1!M>3. p. .").".(>: Notes Alj;. Ill, 

 !'.>3. ]). II: Further Contril*. Fn-sh\v. Plankton Scott. Lochs, p.-nr,, 

 p. 4s7: Phytoplankt. KiiL'l. Lake Di^tr. I'.MIJI. p. 2'.ni : Horiie, Botan. 

 Xotiscr, 1!H3. ].. 32. 



Cells large, about twice as long as broad, not including 

 the processes, constriction slight ; semicells cuneate, 

 broadening upwards ; apex slightly convex, upper angles 

 produced to form long .slender processes, parallel, or 

 very slightly converging with undulate and denticulate 

 margins, upper margin rougher than the lower ; semi- 

 cell with a ring of papillae at its base, of which about 

 7 are visible, and with a circle of large conical granules 

 or flattened verruca? on its apex. Vertical view 4-9- 

 radiate (in British specimens usually 6-9), processes 

 very long and gradually tapering to their apices, which 

 are provided with about 3 minute spines, and w r ith 

 numerous series of denticulations which become larger 

 towards the base of the process ; apex with a circle of 

 large conical nodules or flattened verruca, which usually 

 alternate with the processes. Chloroplast axile, with a 

 central pyrenoid, and a number of ridges. 



Zygospore unknown. 



Length 65-91 u. ; breadth, without processes, 34-46 (JL ; 

 including processes, 128-1 69 pi; breadth of isthmus 

 19-5-26 L. 



