72 BRITISH DESMLDIACE^E. 



ENGLAND.- -Westmoreland ! (Ralfo). Hawkshead, 

 Lancashire ! N. and E. Yorks ! Warwickshire ( Will*). 

 Sussex (Rolfs). Hants! Cornwall! (Rolfs). 



WALES. Capel Curig ! (Cooler. $ Will's) and Moel 

 Siabod, Carnarvonshire ! 



SCOTLAND.- -Sutherland !, Ross, Inverness !, Aberdeen, 

 Kincardine, Forfar, Perth ! (Roy fy Bissett). Plankton 

 of Lochs Fadaghoda, an Sgath, Langabhat, and an 

 Tomain, Lewis, Outer Hebrides; and of Loch nan Eurt, 

 N. Uist, Outer Hebrides ! 



IRELAND.- -Mayo ! Gralway ! Kerry ! Dublin and 

 Wicklow (Archer). Plankton of small lakes in Galway ! 



Geogr. Distribution.- -France. Germany. Austria 

 (var.) and Galicia. Hungary. Norway. Sweden. 

 Denmark. Finland. Poland. S. Russia. Green- 

 land. N. India. E. Africa (var.). United States. 

 Brazil. 



The distinguishing feature of X. cristatum is tlie solitary 

 spine, in a median plane, at each hasal angle of the semicell. 

 The central area is also small, protuberant, and in most type 

 specimens is devoid of either scrohiculations or granules. It 

 is a much less frequent species than X. antilopseum, and never 

 occurs in such abundance. 



Forma angulata West. (PI. CX, fig. 10.) 



X. cristatum forma angulatum West, Alg. W. Ireland, 1892, p. 165, t. 22, 

 13. 



Semicells more angular; cell-wall distinctly punctate. 



Length without spines 51 /u, with spines 67 /u ; 

 breadth without spines 40-43 ju, with spines 62 /* ; 

 breadth of isthmus 12*5 /<; thickness 22*5 /n. 



IRELAND. Lough Aunierin, Gralway. 



Var. leiodermum (Roy & Biss.) Turner. (PL CX, 



. 11.) 



Xanthidium leiodermum Roy & Biss. Japan. Desin. 1886, p. 240, t. 268, 



f. 11. 



X. cristatum var. glabrum Lagerh. Hidr. Amerik. Desm.-fl. p. 245. 

 A', glabrum Lagerh. Krit. Bemerk. Desm. 1887, p. 539 ; De Toni, Syll. Alg. 



1889, p. 930. 

 X. cristatum var. leiodermum (Eov & Biss.) Turn. Freshw. Alg. E. India, 



1893, p. 99, t. 12, f. 33. 



