ON SCOTTISH DESMIDIE^E 239 



straight, semi-cells widening upwards, angles subacute, ends 

 flatly convex ; angles with 3 to 4 rows of crowded, short, 

 simple, acute, stout spines ; end view triangular, or quad- 

 rangular, sides slightly concave, angles acutely rounded, 

 very spiny, 2 to 3 rows of spines across the angles, and a 

 circle of 15 spines around the centre in the triangular 

 form, and of 20 in the quadrangular. Isthmus about half 

 the thickness of the semicell. Membrane smooth. 



L. 57/^; b. 48/x; isth. iS/x; thick. 33^. - from a triangular specimen. 



> 65/^5 59 /*; 24 p; 42 p.- quadrangular 



(Our Plate III. fig. 2.) 



Its nearest ally is S. asperum, Breb. ; but the spines and 

 their arrangement are wholly different. 



Aberdeen Powlair, Slewdrum, Heughhead, Birkhill, 

 Tomachar, Dinnet, Glen Clunie ; Kincardine near Crathes, 

 and pool near Durris Bridge ; Forfar Glen Isla. 



63. S. Hystrix, Ralfs. --Not common. Sutherland, Inverness, 



Aberdeen, Forfar, Perth, Argyle, Arran. 



64. 6". inconspicuum, Nordst. Not common. Sutherland, Ross, 



Inverness, Moray, Aberdeen, Kincardine, Forfar, Perth, 

 Argyle. 



65. S. inflexum, Breb. General. 



66. S. iotanu/n, Wolle. Rare or overlooked. Aberdeen near 



Girnoc; Perth Spital of Glen Shee and Ben Lawers 

 (Mr. W. West). 



67. S. Kjdlmanii, Wille. General, but very sparingly distributed 



on the low grounds ; plentiful on the higher mountains, as 

 Cairngorm, Ben Muichdhui, Lochnagar, etc., near melting 

 snow. Seems too near S. punctulatum, Breb. 



68. X lave, Ralfs. Rare. Sutherland Loch Inver ; Aberdeen 



Birsemore Loch, near Loch Dawan, Tomachar ; Kincardine 

 overflow pool in the Dee, near Durris Bridge. 



69. S. Icevespinnm, Bisset ("Journ. Roy. Micro. Soc." 1884, Plate 



V. fig. 5). Very rare. Arran Goat Fell (Oct. 1882). 



70. S. lanceolatum, Archer. --Not common. Ross, Aberdeen, 



Kincardine, Forfar, Perth. With zygospores, in Aberdeen 

 and Kincardine. 



71. S. leptodermum, Lundell. Very rare. Aberdeen Slewdrum. 



72. S. lunatum, Ralfs. Rare. Ross near Tain; Inverness 



near Brin ; Aberdeen near Alford, south of Birsemore, 

 Dalbagie ; Perth Craig-an-Lochan (Mr. W. West). 



73. 6 1 . Maamense, Archer (Trans. Dub. Micro. Club, i7th December 



1868. S. psendocrenatum, Lundell, 1870). Rare. Its dis- 

 tribution is peculiar, being practically confined to a district 



