STAUEASTRUM. 187 



Length, without spines, 27-32 IJL ; with spines, 37-41 (i; 

 breadth, without spines, 28 y. ; with spines, 34 y* ; 

 breadth of isthmus 9-11 [i. 



WALES.- -Trelleck Common, Monmouth (Turn.). 



Neither St. diplacanthum nor its var. anglicum are very well 

 known, and the figures hitherto published have been very poor. 

 It is almost impossible to get any clear idea of them from the 

 figures of De Xotaris and Turner. 



171. Staurastrum Westii Turner. 

 (PL CLVI, fig. 4.) 



Xftitifijtrinn Westii Turn. Desm. Notes, 1893, p. 345, f. 9. 



Each angle of the cell possesses 5 short thick processes 

 arranged in quincunx, i. e. one in the centre, and one 

 at each of 4 corners, and in addition there are 3 or 4 

 spines on the upper margin of each angle (Turn.). 



Zygospore unknown. 



Length, without spines, 25-28^; including spines, 

 28-32 [i ; breadth, without spines, 18-21 (ji ; with spines, 

 23-26 a ; breadth of isthmus 8-10 u. 



WALES.- -Llyn Padarn, Carnarvonshire (Turn.). 



This species has never been observed since it was described 

 by Turner, and although his description and figure are somewhat 

 meagre, it seems to have very well-defined characters. Turner 

 considered it to be intermediate in form between St. dipla- 

 canth ion De Xot. and St. spongiosum var. GriffitJisianum. 



172. Staurastrum forficulatum Lund. 

 (PL CLIV, figs. 14-16.) 



Staurastrum forficulatum Lund. Desm. Suec. 1871, p. 66, t. 4. f. 5 ; De Toni, 

 Syll. Alg. 1889, p. 1176 ; Roy & Biss. Scott, Desm. 1893, p. 20 ; West & 

 G. S. West, Further Contrib. Plankton Scott. Lochs, 1905, p. 505, t. 7, 

 f. 17; Brit. Freshw. Phytoplankton, 1909, p. 202; Gronblad, Desm. 

 Keuru, 1920, p. 64. 



St. aculeatu/,/ var. bifidum Schmidle, Lappmark Siisswasseralgen, 1898, 

 p. 55, t. 2, f. 44. 



St. forficulatum var. longicorne ibid., p. 55, t. 2, f. 42, 43. 



Cells of medium size, about as long as broad, a little 

 longer than broad, or even up to li times broader than 



