XANTIIID1UM. 55 



WALES.- -Capel Curig lakes, Llyn-y-cwm-ffynon, and 



Glaslyn, Carnarvonshire ! 



t/ 



Geoqr. Distribution.- -Norway. Sandwich Islands. 



t/ t/ 



This is a very distinct variety, at once recognizable by the 

 elongation of the basal portions of the spines, and by the nature 

 of the central protuberance, which is very similar to the 

 marginal spines. It is apparently a very rare variety, but it 

 occurred in great abundance in Llyii-y-cwm-ffynoii, both in 

 the benthos and the plankton. 



Var. irregularius West. (PL CV, figs. 3, 4.) 



X. iii-riwtitiii viir. irregularius West, Alg. W. Ireland, 1892, p. 164, t. 21, f. 1. 



Spines of variable character, often of the nature of 

 emarginate or tridentate warts, often simple with 

 obtuse extremities, generally very irregular in disposi- 

 tion. 



Length (with spines) 1 72-181 /x; breadth (with 

 spines) 110-126 ^ ; breadth of isthmus 4150 /z. 



IRELAND.- -Ballynahinch and Kylemore, Galway ! 



Var. cervicorne AV. & G. S. West. (PI. CVI, figs. 



1-4.) 



X. annatum " finely developed form" Wolle, Desm. U. S. 1884, p. 92, t. 21, 



f. 1. 

 A', armaium var. cervicorne W. & Gr. S. West, Some Desm. U. S. 1898, p. 



300, fig-, xylogr. 3 a-c ; Notes Alg. Ill, 1903,, p. 74 ; Ciisliman. in 



Khodoi-a, vii, 1905, p. 259; W. & G. S. West, Brit. Fresliw. Phyto- 



plankton, etc. 1909, p. 180. 



Larger than the type, with the spines much longer, 

 basal part of spines elongated as in var. fissum, apical 

 part more deeply o-5-furcate and frequently branched 

 in a subdichotomous manner ; teeth of the central wart 

 much larger and more elongated. 



Length (with spines) 242-255 /* ; breadth (with 

 spines) 170-181 p,; breadth of isthmus 47-51 /i. 



WALES.- -In. the plankton of the Capel Curig lakes 

 and Llynau Dy waunedd, Carnarvonshire ! 



SCOTLAND.- -Rhiconich, and in the plankton of Loch 

 Shin, Sutherland ! 



Geoyr. Distribution.- -United. States. 



