EUASTRUM. 59 



with a somewhat dilated extremity ; semicells oblong- 

 rectangular, lateral margins convex and biundulate, 

 the upper undulation larger than the lower one ; apex 

 slightly protracted, truncate and emarginate in the 

 middle, apical angles rectangular. Side view of semi- 

 cell ovate, with a rounded protuberance on each side near 

 the base. Vertical view elliptical, with a rounded pro- 

 tuberance at the middle on each side. Cell- wall smooth. 



Zygospore unknown. 



Length 2<>-4-27/i; breadth 15-6-20//,; breadth of 

 apex lG'8-14'0 p. ; breadth of isthmus 3'5-4'S p. ; 

 thickness 11'5-14*5 //,. 



ENGLAND. Scawfell Pike, Cumberland ! Helvellvii 



i/ 



and Blea Tarn, Westmoreland ! Hawkshead, Lan- 

 cashire ! Keighley Moor, W. Yorks ! Bog near 

 Widdale Beck, and Snaizeholme Fell, N. Yorks ! 



WALES. Bog above Capel Curig lakes, Grlyder Fach 

 (at 2,200 ft.), Llyn-y-cwm-ifynon, and Llyn Teyrn on 

 Snowdon, Carnarvonshire ! 



SCOTLAND. Rhiconich, Sutherland ! Clova, Forfar ! 

 Crianlarich, Perth ! Moidart, Inverness ! W. of Kirk- 

 wall, Orkneys ! 



IRELAND. Poisoned Grlen and Lough Nacung, Done- 

 gal ! Achill Island, Mayo ! Xear Oughterard, Galway ! 

 Carrantuohill, Kerry ! 



G^ot'/i'. Distribution. Bernese Alps. Greenland. 



We always find this small Desmid as an inhabitant of 

 upland districts, and it retains its characters very constantly. 

 It has been known for some time past as Cosmarium Sul- 

 reinschii var. Boldtiana Schmidle, differing from typical 

 C. Subreinschii in the larger and broader central protube- 

 rances, in the relatively wider and more angular apices, and 

 in the apical notch. 



Considering that so far as is known typical C. Subreinscltii 

 does not occur in the British Islands, whereas the Desmid in 

 question is widely distributed and of constant character, we 

 think there is every reason for its specific separation. Not 

 only do we think it is better regarded as a separate species, 

 but we regard the distinct apical emargination, accompanied 

 by a large central protuberance, as characters which must 

 place it in the genus Euastrum. 



