COSMARIUM. 9 



ENGLAND.- -Baildon, Arncliffe, and near Cray Moss, 

 W. Yorks ! Cronkley Fell and Staindale, N/Yorks ! 

 Richmond Park, Surrey ! 



SCOTLAND. Crai'-an-Lochan. Perth ! 



O ' 



IRELAND.- -Cloonee Lough and Kenmare, Kerry! 



This variety differs in the denseness of its granulation, and 

 in the reduction of the granules in the centre of the semicells. 



227. Cosmarium controversum AVost. 

 (PL XCVII, figs. 7 and 8.) 



Cosmarium controversum West, Alg. N. Wales, 1890, p. 289, t. 6, f. 31 

 [figure incorrect] ; Norclst. Index Desm. 1896, p. 81 ; West & Gr. S. 

 West, Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 485 ; 

 Brit. Freshw. Phytoplaiikton, 1909, p. 179 ; Phytoplankton Engl. Lake 

 District, 1909, p. 287. 



Cells fairly large, from ly to 1^ times as long as 

 broad, deeply constricted, sinus narrowly linear with 

 a dilated extremity; semicells pyramidate-trapeziform, 

 basal angles rounded, sides very slightly convex, 

 apical angles rounded, apex broadly truncate. Side 

 view of semicell ovate-elliptic. Vertical view elliptic, 

 with a rather small tumour at the middle on each side. 

 Cell-wall granulate, granules rounded, of uniform size, 

 arranged in decussating oblique series and in indistinct 

 vertical series, about 14 oblique series and 18-19 

 indistinct vertical series (sometimes not at all evident), 

 and from 3035 granules visible at the margin of a 

 semicell ; with a large area in the centre of the 

 semicell in which there are hexagons of conspicuous, 

 rounded scrobiculations between the granules. Cliloro- 

 plasts axile, with two pyrenoids in each semicell. 



Z y gospor e unkno w n . 



Length 90-96 ^ ; breadth 72-77 ft ; breadth of 

 isthmus 22-32 p; thickness 45 p.. 



ENGLAND.- -Plankton of Grasmere, Westmoreland ! 



"WALES.- -Capel Curig, Carnarvonshire! 



SCOTLAND. Plankton of Loch Fadaghoda, Lewis, 

 Outer Hebrides ! 



The original figure of this Desmid represented the species 

 very indifferently, and the large, scrobiculated central area 



