196 BRITISH DESMIDIACE^. 



Length, without processes, 51 [x ; including processes, 

 65 pi ; breadth, without processes, about 42-46 (JL ; in- 

 cluding processes, 84*5-90 (JL ; breadth of isthmus 12 (JL. 



SCOTLAND.- -Plankton of Loch Shin, Sutherland ! 



SPECIES TO BE ENQUIRED INTO. 



STAURASTRUM MESOLEIUM Arch, in 'Ann. Mag. Nat. Hist.' v. 

 13, ser. 5, no. 74, 1884, p. 145 ; Cooke, ' Brit. Desm.' 1887, p. 190 ; 

 Eoy & Biss. ' Scott. Desm.' 1893, p. 190. "About medium sized, 

 triangular in end view, in front view the angles a little produced, 

 slightly spinulose. Resembling St. oligacanthum of Nordstedt, 

 but not of de Brebisson." Size ? 



Hob. Ireland : Gallery Bog, Connemara. Scotland : Scots- 

 ton Moor. 



STAURASTRUM REPANDUM (Perty) Rabenh. 'Flor. Eur. Alg.' 

 1868, p. 221 ; De Toni, 'Syll. Alg.' 1889, p. 1143. Phycastrum 

 (P achy actinium) repandum Perty, ' Kleinst. Lebensf.' 1852, p. 210, 

 t. 16, f. 26. " In front view $"' long, each semicell prolonged 

 at the lateral angles into sharp points ; dorsal margin sloping 

 gently downwards ; vertical view triangular, angles and sides 

 almost equal, angles drawn out into sharp points. Breadth, 

 including the acute points, oV". 



Hob. Scotland : Glen Callator, Aberdeen (Roy & Biss.). 

 Switzerland. 



STAURASTRUM STRENSALLENSE Turn. 'Alg. E. India,' 1893, 

 p. 113, t. 17, f. 1. Of medium size, almost as long as broad; 

 sernicells depressed ovate, dorsal margin gently convex, ventral 

 margin rounded and inflated, angles rounded; cell- wall covered 

 densely with spines, disposed in 9 or 10 transverse series, that 

 part near the isthmus being, however, smooth ; sinus acute, 

 opening widely. In vertical view triangular, sides slightly 

 concave, angles broadly rounded. Length 65 /m ; breadth 63 ^ ;. 

 breadth of isthmus 21 /u ; length of spines 3-6 /u. 



Hob. England : Strensall Common, Yorkshire. 



STAURASTRUM TRACHYNOTUM West, 'Alg. W. Ireland,' 1892, 

 p. 176. S. saxonicwn Reinsch, ' Spec. Gen. Alg.' 1867, p. 127, 

 t. 24 C, f. 1-4. Var. ANNULATUM West, 'Alg. W. Ireland,' 1892, 

 p. 176, t. 24, f. 16. Cells slightly longer than broad, deeply 



