50 BRITISH DESMIDIACE^. 



Length 39 (JL ; breadth 40 [i ; breadth of isthmus 

 22'5 p. 



IRELAND.- -In small lakes, Clifden to Roundstone, 

 Galway ! 



74. Staurastrum trachygonum West. 

 (PL CXXXIX, fig. 3.) 



St. trachygonum West, Alg. W. Ireland, 1892, p. 176, t. 23, f. 5. 



Cells small, a little longer than broad, constriction 

 moderately deep, sinus fairly open ; semicells sub- 

 elliptical, apex truncate, cells provided with spines, 

 some of which are truncate, round the angles and on 

 the apex ; in vertical view triangular, sides very slightly 

 concave, angles rounded, the smooth apex provided 

 with a circle of short spines. 



Zygospore unknown. 



Length 32 '5 (JL ; breadth 28 \JL ; breadth of isthmus 



7'5jJi. 

 IRELAND. Kylemore, Co. Galway ! 



75. Staurastrum spiniferum West. 

 (PI. CXXXIV, fig. 7.) 



St. spiniferum West, Alg. N. Wales, 1890, p. 16, f . 20 ; Freslnv. Alg. Maine, II, 

 1891, p. 3 ; West & G. S. West, Brit, Freslnv. Phytoplankt. 1909, p. 202. 



Cells small, slightly longer than broad, deeply con- 

 stricted, sinus open and acute; semicells elliptical, with 

 about 8 spines round the periphery of each. Vertical 

 view triangular, sides very slightly concave, with a spine 

 at each angle and two others projecting from each side, 

 and with two or three scattered spines also on the apex. 



Zygospore unknown. 



Length, without spines, 25 [JL ; breadth, without 

 spines, 22 (x ; breadth of isthmus 7*5 [Jt ; length of spines 

 about 5(ji. 



WALES.' Ffestiniog, Merioneth ! 



Geogr. Distribution.- -United States. 



