ON SCOTTISH DESMIDIEiE 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/x; b. 48/x; isth. 18/x; thick. 3 3^. — from a triangular specimen. 



» 6 5/*; » 59/*; » 24^; „ 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, Birkhili, 

 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. S. inconspicuum, Nordst. — Not common. Sutherland, Ross, 



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



Argyle. 



65. 6". inflexum, Breb. — General. 



66. S. iotanum, Wolle. — Rare or overlooked. Aberdeen — near 



Girnoc ; Perth — Spital of Glen Shee and Ben Lawers 

 (Mr. W. West). 



67. S. Kjellmanii, 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. £. Iceve, Ralfs. — Rare. Sutherland — Loch Inver ; Aberdeen — 



Birsemore Loch, near Loch Dawan, Tomachar ; Kincardine 

 — overflow pool in the Dee, near Durris Bridge. 



69. 6". icevespinum, Bisset ("Journ. Roy. Micro. Soc." 1884, Plate 



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



70. S. la?iceolatum, Archer. — Not common. Ross, Aberdeen, 



Kincardine, Forfar, Perth. With zygospores, in Aberdeen 

 and Kincardine. 



71. S. leptodermuni, Lundell. — Very rare. Aberdeen — Slewdrum. 



72. S. liuiatum, Ralfs. — Rare. Ross — near Tain ; Inverness — 



near llrin : Aberdeen — near Alford, south of Birsemore, 

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



73. S. Afaamense, Archer (Trans. Dub. Micro. Club, 17th December 



1868. S. pseudocrenatum t Lundell, 1870). — Rare. Its dis- 

 tribution is peculiar, being practically confined to a district 



