STAURA STRUM. 127 



SCOTLAND. Sutherland, Boss, Inverness, Aberdeen, 

 Kincardine, Forfar, Perth, Dumbarton, and Bute (Rot/ 

 $ Bissett). 



Geogr. Distribution.--SpiizbeYgeii. lS T ova Zembla. 

 N. Russia, Brazil. 



We have not seen this variety, and we are inclined to think 

 that Messrs. Roy & Bissett have referred to it all the forms of 

 St. Capitulum which came under tlieir notice. It differs so 

 little from typical St. Capitulum that it is hardly worth the 

 separation. 



3. Staurastrum pileolatum Breb. 

 (PI. CXVIII, figs. 11-13.) 



Staurastrv.ru pileolatum Breb. in Ealfs' Brit. Desm. 1848, p. 215, t. 35, 

 f. 22 [figure inaccurate] ; Arch, in Pritch. Infus. 1861, p. 740 ; Eabenh. 

 Flor. Europ. Alg. Ill, 1868, p. 220 ; Cooke, Brit. Desm. 1887, p. 160, 

 t. 55, f. 1 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 216 ; De Toni, Syll. 

 Alg. 1889, p. 1191 ; West, Alg. N. Wales, 1890, p. 294 ; Koy & Biss. 

 Scott. Desm. 1893, p. 241 ; Nordst. Index Desm. 1896, p. 200. 



St. amoenum Hilse var. brasiliense Borg. as recorded by West, Alg. W. 

 Ireland, 1892, p. 179, t. 23, f. 9. 



St. pileolatum Breb. var. brasiliense (Borg.) Lutkem. as recorded by W. 

 & G. S. West, Alga-fl. Yorks. 1901, p. 107 ; Notes Alg. Ill, 1903, p. 11 

 (sep.) ; Freshw. Alg. Orkneys and Shetlands, 1905, p. 28. 



Cells rather small, about twice as long as broad, 

 slightly constricted, sinus a small acute-angled notch ; 

 semicells rectangular- subcampanulate, base broad and 

 very slightly tumid-emarginate just above the sinus 

 (caused by a ring of emarginate verrucse or short 

 ridges which completely encircle the base of the semi- 

 cell), sides slightly retuse near the base, after which 

 they diverge very slightly upwards, apex concave, 

 apical angles rounded-conical and minutely granulate, 

 each with about 5 concentric rings of small granules, 



those near the basal verrucas becoming- very minute. 



. " 



Vertical view of basal part of semicell circular with a 

 crenate margin ; crenas 18-21, bluntly rounded ; vertical 

 view of apical part of semicell triangular (rarely quad- 

 rangular) with acutely-rounded angles and very slightly 

 concave sides. 



Zygospore globose, furnished with a few short, stout 

 spines, 2-3-fid at the apex. 



