268 BRITISH DESMIDIACE^E. 



irregular. Vertical view elliptic, granules forming a 

 broad median band from pole to pole (4-5 visible at 

 the margin of each pole), disposition of granules some- 

 what irregular, but generally showing indications of 

 4-5 very irregular series. Cell-wall finely scrobiculate, 

 and distinctly thickened in the centre of each semicell. 

 Chloroplasts parietal, forming 4-6 broad, irregular 

 bands extending from base to apex of each semicell ; 

 pyrenoids rather small and numerous, 9-11 in each 

 chloroplast. 



Zygospore unknown. 



Length 1 78-222 /x; breadth 98-130 /A; breadth of 

 isthmus 30-47 p,; thickness 74-94/1. 



ENGLAND.- -Bowness, Westmoreland! (Italfo). Great 

 Sh minor Fell and Strensall, N. Yorks ! New Forest, 

 Hants ! 



SCOTLAND.- -Rlriconich, Sutherland ! Khoil, Aberdeen 

 (Roy ft Bissett). Ben Lawers and Craig-an-Lochan, 

 Perth ! Plankton of Loch Shiel, Inverness ! Plankton 

 of Loch Fadaghoda, Lewis, and Loch Xan Eun, 

 N. Uist, Outer Hebrides ! 



IRELAND.- -Near Sproule's Lough, Donegal ! Bally - 

 nahinch, Galway ! Adrigole, Kerry ! Very rare in 

 the plankton of small lakes between Clifden and Round- 

 stone, Galway ! 



Geogr. Distribution.- -France. Germany. Galicia 

 in Austria. Silesia (var.). Italy. Norway. Sweden. 

 United States. Brazil. 



Cosmarium ovale stands quite alone among European species 

 of the genus, not merely on account of its size, but also with 

 regard to its granulation. In the United States it is accom- 

 panied by another allied species of almost equal size 

 C. (lentcdum Wolle (consult West & G. S. West, ' Some 

 N. Amer. Desm/ 1896, p. 249, t. 15, f. 10-11). There are in 

 all four known members of the " C. ovale- group," the two 

 remaining species being C. denticulatumTSorge (' Austral. Siiss- 

 wasserchlor.' 1896, p. 19, t. 3, f. 31) and C. splendidum Borge 

 (' Alg. erst, Regiiell. Exped. II, Desmid/ 1903, p. 99, t, 3, 

 f. 27), both of which are amongst the largest and handsomest 

 species of the genus. The former possesses numerous, short, 



