152 BRITISH DESMIDIACE^E. 



WALES.- -Llyn-y-cwm-ifynon ! and Capel Curig ! (Cooke 

 <& Witts), Carnarvonshire. Dolgelly (Ralfs), Merioneth. 

 In the plankton 



SCOTLAND.- -From several localities in Aberdeen ; 

 Nigg, Craithes, and Cuiran, Kincardine ; Glen Coe, 

 Argyle (Roy & Biss.). Rhiconich, Sutherland ! Loch 

 Bairness, Inverness ! Lochs Fadaghoda and Stranabhat, 

 Lewis, Outer Hebrides ! In the plankton ! 



IRELAND. --Dungloe, Donegal! Derrvclare Lough, 

 Athrey Lough, Ballynahinch, and in Lakes, Clifden to 

 Roundstone, Galway ! Adrigole, Co. Cork ! In the 

 plankton ! 



Geogr. Distribution.- -Fiance. Germany. Galicia and 

 Austria. Italy. Norway. Sweden. Finland. Denmark. 

 Bornholm. Faeroes. Greenland. Japan. Australia. 

 Central Africa, United States. 



St. Arachne is a most characteristic species easily recognised 

 by its long slender processes, which, when the individual is in an 

 oblique position, give the appearance of a spider with long 

 untidy legs. It is not at all general in its distribution, but 

 sometimes occurs in profusion in the western areas of the British 

 Isles, having a decided preference for the older palaeozoic and 

 precambrian formations. 



Var. curvatum W. & G. S. West, (PL CL, fig. 2.) 



St, Arachne var. curt-alum West & G. 8. West, Scott. Freshw. Plankt. I, 

 1903, p. 549, t, 18, f. 9 ; Further Contrib. Plankton Scott. Lochs, 1905, 

 p. 487, t. 1, No. 2, f. 5. 



Processes bent slightly, but distinctly upwards ; in 

 end view 4- or 5 -radiate. 



Length 30 pi ; breadth, without processes, 18 pi ; with 

 processes, 57-70 [x ; breadth of isthmus 9 pi. 



SCOTLAND.- -Plankton of Lochs nan Cuinne and Ruar, 

 Sutherland ! 



This variety is either 4- or 5-radiate, and differs from all other 

 forms of St. Arachne in the outwardly curved processes. 



Var. arachnoides W. & G. S. West. (PL CL, fig. 3.) 



St. arachnoides West, Alg. W. Ireland, 1892, p. 180, t, 24, f. 4. 



St. Arachne var. arachnoides West & G. S. West, Alg. N. Ireland, 1902, p. 56. 



