62 BRITISH DESMIDIACK.E. 



Length without spines 21-30 JJL ; breadth without 

 spines 19-28/x; length of spines 6'5-8/x,; breadth of 

 isthmus 8-1 1/x; thickness 12-16/x; cliam. zygosp. 

 without spines 25-26 /x,, with spines 66-68 p.. 



ENGLAND.- -Near Bowness, Westmoreland (Sissett). 



WALES.- -Moel Siabod, Carnarvonshire! Ehos Groch 

 Boo*, Radnorshire ! 



O ' 



SCOTLAND.- -Cammie in Strachan, Kincardine; zygos- 

 pore from near Aboyne, Aberdeen (Roy Bissett). 

 Grarynahine, Lewis, and Harris, Outer Hebrides ! 



IRELAND.- -Lakes between Clifden and Roundstone, 

 Gal way ! Cromagloun, and Tore Mountain, Kerry ! 

 Castle town, Cork! 



Geogr. Distribution.- -Patagonia. 



X. Smithii is a very rare species which apparently only occurs 

 in abundance in a few districts in North Wales, the Avest of 

 Ireland, and the Outer Hebrides. It is one of the most 

 distinctive species of the genus and cannot well be confounded 

 with any other. 



t/ 



Var. majus (Ralfs) nol. (PI. CVIII, fig. 5.) 



XantJiidinm ? octocorne (Ehrenb.) Ralfs var. major Kalfs, Brit. Desm. 



1848, p. 116, t. 20, f. 2/-i. 

 Arfhrodesm-us octocornis Ehrenb. var. major Cooke, Brit. Desm. 1887, p. 



135, t. 47, f. 2 a, fc, c, f, g ; Lund. Desm. Suec. 1871, p. 56; Nordst. 



Norges. Desm. 1873, p. 25 ; De Toni, Syll. Alg. 1889, p. 1063 ; Eoy eV 



Biss. Scott. Desm. 1894, p. 41 [but not t, 2, f. 20] ; Eichler in Pamiet. 



Fizyograf. Akad. Umiej. Krakow, xiii, 1895, p. 60. 



Slightly larger than the type, sides and apex of 

 semicells rather more concave, spines often shorter 

 and stouter, from one to three inserted at each angle, 

 and often of different lengths : central area of semicell 



o 



slightly thickened, but not protuberant. 



Length without spines 26-30 p. ; breadth without 

 spines 27-32 /x; breadth of isthmus 9-12 /x ; thickness 

 12-16 p. ; length of spines 4-9 '5 p.. 



WALES. Dolgelly, Merioneth (Italfx). 



SCOTLAND.- -Orkneys, Sutherland!, Eoss, Inverness, 

 Aberdeen, Kincardine, Forfar, Perth, and Argyll 

 (Roy $ Bissetf). 



