STAUEASTRUM. 139 



9. Staurastrum coarctatum Brcb. 

 (PI. CXIX, fig. 8.) 



Staurastrum coarctatum Breb. Liste Desm. 185H, p. 144, t. 1, f. 29 ; Arch. 

 in Pritch. Infus. 1861, p. 740 ; Eabenh. Flor. Exirop. Alg-. III, 1868, 

 p. 220; De Toni, Syll. Alg. 1889, p. 1187; Eoy & Biss. Scott. Desm. 

 1893, p. 179 ; Nordst. Index Desm. 1896, p. 76. 



Cells small, a little broader than long, very deeply 

 constricted, sinus open and acute-angled ; semicells 

 transversely oblong, with the angles very broadly 

 rounded and slightly divergent, apex faintly retuse. 

 Vertical view triangular, with broadlv rounded angles 



o / 



and concave sides. Cell-wall smooth. 



Zygospore unknown. 



Length 33-3/1,; breadth 38-40 /x; breadth of 

 isthmus 95 p.. 



SCOTLAND. Cammie in Strachan, Kincardine (Roy 

 $ Bissett). 



Geogr. Distribution.- -France. Sweden (var.). Brazil 

 (var.). 



The typical form of this species lias only once been observed 

 since its original discovery bv Brebisson. in 1856. It is 



O e/ e/ 



recorded hy Messrs. Roy and Bissett as "very rare" in one 

 locality in Kincardine. 



Var. su.bcu.rtum Xordst. (PI. CXIX, figs. 9, 10.) 



St. coarctatum var. subcurtum Nordst. in Botan. Notiser, 1887, p. 158 ; 

 Fresh w. Alg. N. Zeal. 1888, p. 41, t. 4, f. 20; West, Alg. N. Wales, 

 1890, p. 293, t. 5, f. 8 ; Sehmidle, Lappmark Siisswasseralgeii, 1898, 

 p. 57. 



Cells with a wider and more obtuse sinus, isthmus 

 relatively broader and a little elongated ; semicells less 



il O 7 



wide than in the type, lateral angles shorter and not 

 divergent, apex straight or very faintly convex. 



Length 20-28 //,; breadth 16-23 p. ; breadth of 

 isthmus 6-12 /x. 



WALES.- -Capel Curig, Carnarvonshire ! 



Geogr. Distribution. Norway (Lappmark). Xew 

 Zealand. 



This variety should be compared with St. mnticum, from 



