112 BRITISH DESMTDIAOEJ1. 



long straight spine. Vertical view elliptic, with one 

 straight spine showing at each rounded pole. 



Zygospore globose or subglobose, furnished with a 

 few simple straight spines, about 8 of which show at 

 the periphery ; wall of spore with a broad and slightly 

 projecting thickening at the base of each spine. 



Length without spines 17-2 7 /A, with spines 30- 

 42 /z ; breadth without spines 14'3-19 /x, with spines 

 28-35 '5/i; breadth of isthmus 4'2-7*6 \L ; thickness 

 G'5-9//,; cliam. zygosp. without spines 15^, with 

 spines 28 /*. 



ENGLAND.- -Cumberland ! Westmoreland ! (Rolfs ; 

 Bissett). W. and N. Yorks ! Burnham Beeches, 

 Bucks! Gloucester (R 'alfs). Surrey! (Rnlfs) ; zygo- 

 spores from Puttenham Common ! Sussex (Ralfs). 

 Hants! (Half a) . Devon! Cornwall! (Ralfs). 



WALES.- -Llyn Bodgynwydd, Capel Curig (Cooler 

 fy Wills), Llyn Ogwen, Llyn Idwal, Llyn Bochlwyd, 

 Glyder Fach (at 2200 " ft.), Llyn-y-cwm-ifynon, 

 Snowdon, and Moel Siabod, Carnarvonshire ! 



SCOTLAND. General ! ; zygospores from Aberdeen, 

 Kincardine, and Perth (Roy $ Bissett). Outer 

 Hebrides ! Scarce in the plankton ! 



IRELAND.- -Donegal ! Londonderry ! Dublin and 

 "Wicklow (Archer). Gal way ! Mayo! Kerry! Cork! 



Geogr. Distribution.- -France. Germany. Poland. 

 Austria and Galicia. Italy. Norway. Sweden. 

 Denmark. Bornholm. Finland. N.Russia. Faeroes. 

 Iceland. Greenland. Mongolia. Japan. Burma. 

 Ceylon, Australia. United States. 



A. octocornis is a very characteristic species with a wide 

 distribution. It scarcely needs comparison with any other 

 species, and in the British Islands it exhibits little variation. 

 The a /3 major Ralfs ' ; has been transferred to Xanthidium 

 Smithii, a Desmid to which we think it more rightly belongs 

 (consult page 62). 



A trigonal variety (var. trlgonum) was described by Boldt 

 from Greenland in 1888, and has since been found in West 

 Greenland by Larsen. 



Liitkemuller (' Desm. Millstattersees/ 1900, p. 13) has given 



