COSMAKIUM. 17 L 



ventral margin always more convex than the dorsal 

 margin. Side view of semicell circular. Vertical view 

 elliptic, ratio of axes 1 : 1'57. Cell-wall colourless and 

 finely punctate. Chloroplasts axile, with one central 

 pyrenoicl. 



Zygospore globose or angular-globose, smooth. 



Length 34'5-41/x; breadth 25-3 1/x; breadth of 

 isthmus 7-8* 7 ft; thickness 18-19 /x; diam. zygosp. 

 31*535 JJL. 



ENGLAND. Bowness, Westmoreland ! Widdale Fell, 

 W. Yorks ! Pilmoor, X. Yorks ! Pnttenham Common, 

 Surrey ! 



WALES. Llyn Bodgynwydd, Capel Curig, and Llyn- 

 y-cwm-ffynon, Carnarvonshire ! 



SCOTLAND.- -Near Alford, and south of Birsemore, 

 Aberdeen; Buchaiity, Perth (Roy Bissett). Khi- 

 conich, Sutherland ! Xot uncommon in the plankton 



of Sutherland, Inverness, Ayrshire, and the Outer 



t> 



Hebrides ! 



IRELAND.- -Lough Gartan and near Lough Magrath, 

 Donegal ! Ballynahinch, Clifden, and Lough Aunierin, 

 Galway ! Cromagloun, Tore Mt., and Adrigole, Kerry ! 

 Lough Derryadd, Armagh ! 



Geoc/r. Distribution --QeYmany. Galicia in Austria. 

 Poland. Xorway. India. Ceylon. Burmah. Siam. 

 Australia. Central Africa. Madagascar. United 

 States. Patagonia. 



C. contraction is a somewhat rare British species, although 

 it sometimes occurs in abundance in the plankton. It is very 

 deeply constricted, the isthmus forming a narrow neck, and 

 the sinus is widely open. The semicells in the front view are 

 subelliptic in form, the low^er margin being more convex than 

 the upper one. 



The Desmicl described and figured by Turner ('Freshw. 

 Alg. E. India/ 1893, p. 48, t, 7, f. 38, t. 9, f. 21) as C. con- 

 tractum var. punctatum does not belong to this species. 



Forma Jacobsenii (Roy) nol. (PL LXI, f. 26.) 



Cosmarium moniliforme (Turp.) Ealfs forma elliptica Nordst. Norges. 



Desm. 1873, p. 22. 

 C. moniliforme Jacobs. Desm. Daneni. 1876, p. 200, t. 8, f. 24. 



