28 BRITISH DESMIDIACE^E. 



57. Staurastrum Ungeri Reinsch.' 

 (PL CXXXIII, fig. 5.) 



Staurastrum Ungeri Reinsch, Spec. Gen. Alg. 1867, p. 24, t. 24 B, I, f. 1-6 ; 



De Toni, Syll. Alg. 1889, p. 1152 ; Roy & Biss. Scott. Desm. 1894, p. 26 

 Didymidium (Staurastrum) Ungeri Reinsch, Algenfl. Frank. 1867, p. 174,. 



t. 11, f. 3. 

 Staurastrum acanthophorum West & G. S. West, Alg. Madag. 1895, p. 72,. 



t. 8, f. 10 (var.). 



Cells small, about as long as broad, deeply con- 

 stricted, isthmus one- third or more the diameter of 

 the cell, sinus acute-angled ; semicells elliptical, dorsal 

 and ventral margins almost equally convex, lateral 

 angles ending in a stout spine, in length one-third or 

 one-fourth the diameter of the cell. Vertical view tri- 

 angular or quadrangular, lateral margins straight or 

 slightly concave, angles obtusely rounded, each with a 

 stout spine. Cell- wall provided with numerous short 

 conical spines, irregularly scattered, and about one- 

 third or one-fourth the length of the larger angular 

 spines. 



Zygospore unknown. 



Length = breadth = 27 or 28 \L ; length of angular 

 spines 8 \L . 



SCOTLAND.- -Loch Ruthven, Inverness; old channel 

 of Dee, below Aboyne, Aberdeen ; Keiloch, Kincardine 

 (Roy & Biss.). 



Geogr. Distribution. Germany. Switzerland (var.). 

 Madagascar (var.). 



58. Staurastrum tunguscanum Boldt. 

 (PL CXXXIII, fig. 4.) 



Staurastrum tunguscanum Boldt, Sibir. Chlorophy. 1885, p. 114, t. 5, f. 22 ; 

 De Toni, Syll. Alg. 1889, p. 1146; Gutw. Flor. Glon. Okolic Lwowa, 

 1891, p. 66. t. 3, f. 12 (forma) ; Borge, Siissw. Chlor. Archang. 1894, 

 p. 37 ; West & G. S. West, Alg. S. England, 1897, p. 493. 



Cells small, slightly longer than broad, deeply con- 

 stricted ; sinus acute-angled, opening widely ; semicells 

 subtriangular, directed away from each other, lateral 



