STAURASTRUM. 151 



16. Staurastrum pachyrhynchum Nordst. 

 (PI. CXXI, figs. 8, 9.) 



Stair/'astrnm pachyrhynch2tm Nordst. Desm. Arctose, 1875, p. 32, t. 8, f . 34 ; 

 Boldt, Siber. Chlorophy. 1885, p. Ill ; De Toni, Syll. Alg. 1881), p. 1185 ; 

 Borg-e, Bidr. Siber. Chlor. 1891, p. 9, t. 1, f. 5 ; Roy & Biss. Scott. Desm. 

 iv. '3, p. 241 (sep. p. 23) ; Borg-. Ferskv. Alg. Ostgronl. 1894, p. 24, t. 2, 

 f . 19, 20 [forms] ; Nordst. Index Desm. 1896, p. 193 ; W. & G. S. West, 

 Alg. S. England, 1897, p. 494 ; Some Desm. U. S. 1898, p. 314 ; Larsen, 

 Freshw. Alg. E. Greenland, 1901, p. 99 ; Ferskvandsalg. Vest-Gronl. 

 1907, p. 351. 



Cells somewhat small, about as long as broad, deeply 

 constricted, sinus open, subrectangular or acute-angled ; 

 semicells subelliptic or elliptic-subtriangular, dorsal 

 margin subtruncate, convex or strongly convex, angles 



cj O i/ O 



very slightly (almost imperceptibly) produced, rounded- 

 obtuse, usually with a very faint upward tilt. Vertical 

 view o-5-angular, sides concave, angles rounded-obtuse. 

 Cell-wall smooth or very delicately punctate, very 

 strongly thickened at the angles. 



Zygospore unknown. 



Length 28-45 p.; breadth 22-45 p.; breadth of 

 isthmus 8-1 5 {JL. 



ENGLAND.- -Thursley Common, Surrey ! Xew Forest, 

 Hants ! 



W,-\LKs.--Capel Curig, Carnarvonshire! 



SCOTLAND.- -Slewdrum and Heughhead near Aboyne, 

 Aberdeen (Roy $ Bissett). 



IRELAND.- -Dublin and Wicklow (Archer). 



Geonr. Distribution. Germany. Austria (var.). 



t/ e/ 



Sweden. Poland (var.). Nova Zembla. Spitz- 

 bergen. Greenland. Siberia. United States. Para- 



o 



guay (form). 



In British and American specimens we have found the 

 thickened angles of the semicells directed horizontally in the 

 front view. In arctic specimens they appear usually to have 

 a faint upward or divergent tilt. In. a form described by 

 Raciborski as u var. convergens" (Racih. ' Desm. Nowe/ 1889, 

 p. 98, t. 7, f. 14), and known to occur in Poland, Grermany, 

 and Austria, the angles of the semicells are decidedly con- 

 vergent. 



We do not agree with Stockmayer (in ' Osterr. botan. 



