142 BRITISH DESMIDIACE^l. 



is exquisite, and is one of the most constant characters of the 

 species. It is confined to the western part of the British Isles. 



141. Staurastrum anatinum Cooke Wills. 

 (PL CXLVI, fig. 7 ; PL CXLVII, fig. 1.) 



Staurastrum anatinum Cooke & Wills, Cooke in Grevillea, 1880, p. 92, 1. 139, 

 f. 6 ; Wills in Midland Naturalist, 1881, p. 18, t. 5, f. 3 ; Turner, Alg. 

 Strensall Common, 1883, f. 4 ; Wolle, Desm. U. S. 1884, p. 139, t. 51, 

 f. 1, 2 ; Cooke, Brit. Desm. 1887, p. 176, t. 61, f. 2 ; De Toni, Syll. Alg. 

 1889, p. 1221 ; West, Freshw. Alg. N. Wales. 1890, p. 280, t. 5, f. 12 ; 

 Roy & Biss. Scott. Desm. 1893, p. 16 ; W. & G. S. West, Alg. S. England, 

 1897, p. 496 ; Alg. N. Ireland, 1902, p. 54, t. 1, f. 24, 25 ; Scott. Freshw. 

 Plankton, I, 1903, p. 530 ; Further Contrib. Plankt. Scott. Lochs, 1905, 

 p. 487 ; Brit. Freslnv. Phytoplankton, 1909, p. 174 and 168 ; Borge, 

 Botan. Notiser, 1913, p. 50. 



Cells large, about 1 \ times broader than long, including 

 the processes, deeply constricted, sinus acute, and 

 opening widely; semicells subfusiform, ventral margin 

 more convex than the dorsal, upper angles produced to 

 form fairly long stout divergent processes, provided 

 with several series of well-marked denticulations and 

 tipped with two or three strong spines ; apex of semi- 

 cell slightly convex, and verrucose. Vertical view tri- 

 angular or quadrangular, sides straight or very slightly 

 concave, angles produced to form processes, lateral 

 margins verrucose, with another series of about 6 emar- 

 ginate verrucae just within each margin. 



Zygospore unknown. 



Length, without processes, 33-46 [i ; with processes, 

 50-65 pi ; breadth, with processes, 80-1 13 pi; breadth 

 of isthmus 10-1 5 '5 pi. 



ENGLAND.- -Plankton of Buttermere, Crummock Water 

 and Ennerdale Water, Cumberland ! Plankton of Red 

 Tarn, Codale and Easedale Tarns, Westmoreland ! New 

 Forest, Hants ! 



WALES. Capel Curig ! (Cooke & Wills) and Llyn-y- 

 cwm-ffynon, Carnarvonshire ! In the plankton ! 



SCOTLAND. Slewdrum, Blair Glas, between Loch 

 Kinord and Cambas, Aberdeen ; near Curran in 

 Strachan, Kincardine ; Glen Coe, Argyle (Roy & Biss.). 



