24 BRITISH DESMIDIAOEJ!. 



mucli broader than in the type ; sinus obtuse, often 

 rounded. 



Length 37-52 p, ; breadth 19-27 p ; breadth of 

 isthmus 1 2-14'S ^u. 



SCOTLAND.- -In the plankton of Loch Fadaghoda, 

 Lewis, Outer Hebrides ! 



IRELAND.- -In the plankton of several small lakes 

 between Clifden and Roundstone, and also in the 

 plankton of Lough Corrib, Galway ! 



Geogr. Distribution.- -Australia, (in plankton). 



This variety appears to be mostly a plankton-form. It is 

 readily distinguished by the slight angularity of the apices 

 and the wide isthmus. The widest part of the semicell is 

 nearer the base than the apex, and the upper half is commonly 

 rounded-conical in form. 



61. Cosmarium alpestre Roy & Biss. 

 (PL LXVII, fig. 14.) 



Cosmarium alpestre Roy & Biss. Scott. Desm. 1894, p. 41, t. 1, f. 6. 



Cells large, a little longer than broad, very slightly 

 and broadly constricted ; semicells subsemicircular, 

 sometimes faintly flattened at the apex. Side view of 

 semicell subsemicircular. Vertical view very broadly 

 elliptic, ratio of axes 1 : 1'15. Cell- wall densely and 

 finely punctate, with a row of rather larger punctse 

 bordering the broad isthmus on each side. 



Zygospore unknown. 



Length 90-105 p, ; breadth 75-90 p. ; breadth of 

 isthmus 79 JJL ; thickness 60 p.. 



SCOTLAND.- -Press Whin on the north side of Morven, 

 Aberdeen ; North-west side of Glas Mhoel, above the 

 Cairnwell, Perth (Roy $ Bissett). 



We have not seen this species which Messrs. Eoy & Bissett 

 state to be very rare and not hitherto found under 2,000 ft. 

 Its relative breadth and the slightness of its constriction at 

 ouce distinguish it from C. connatum Breb. In outward form 

 it most nearly resembles the Desinid described by Delponte 

 as Dysphinctium ellipticum (fide Delp. ' Desm. subalp./ 1877, 

 p. 134, t. 21, f. 14). 



