16 BRITISH DESMIDIACE^:. 



Cells small, about as long as broad, or up to Ij times 

 longer than broad, excluding the spines, deeply con- 

 stricted, sinus subrectangular, often acute at the apex, 

 opening broadly ; semicells obversely subsemicircular, 

 ventral margin very strongly convex, dorsal margin 

 nearly straight, or even slightly concave, upper angles of 

 semicells somewhat acutely rounded, with a long erect 

 spine projecting from each. Vertical view triangular, 

 lateral margins slightly concave, angles broadly rounded, 

 spines very small (as a result of foreshortening). 



Zygospore of type unknown, but probably more or 

 less rounded, with a few short stout conical spines (cf. 

 zygote of var. Spencerianum, PL CXXX, fig. 9). 



Length, without spines, 21-29*5 [j, ; breadth 20-22 '5 pi; 

 breadth of isthmus 6 '6-9 '2 (JL ; length of spines 8-13 [i. 



ENGLAND. Strensall Common, N. Yorks (W. B. 

 Turn.). Eiccall Common, E. Yorks ! Dartmoor, 

 Devonshire ! Gunwen Moor, Cornwall ! 



WALES.- -Bettws-y-coed (Roy), and Capel Curig ! 

 Carnarvonshire. 



SCOTLAND. General (Roy & Biss.). Rhiconich, 

 Sutherland ! 



IRELAND.- -Lough Anna and near Lough Magrath, 

 Donegal ! Dublin and Wicklow (Arch.). Lough 

 Derryadd, Armagh ! 



Geogr. Distribution. Austria. Norway. Finmark. 

 Sweden. Bornholm. Finland. Poland. Central China. 

 Japan. Turkey in Asia. Ceylon. Australia. New 

 Zealand. United States. Brazil. 



St. connatum is widely distributed but is not quite as common 

 as some of the other allied species. The form of its semicells 

 and its long erect spines readily distinguish it from all other 

 Desmids of the Staurastrum dejectum series. 



50. Staurastrum jaculiferum West. 

 (PL CXXX, figs. 17, 18 ; PL CXXXI, figs. 1-3.) 



Staurastrum jaculiferum West, Alg. W. Ireland, 1892, p. 172, t. 22, f. 14; 

 Racib. Desra. Tapakoomas, 1895, p. 34 ; Borg. Freshw. Alg. Faeroes, 



