106 BllITISH FBESHWATEE EHIZOFODA. 



8, p. 8; Daday in Termesz. Fiizetek, XX (1897), p. 154 

 ScHAUDiNN in Dentscli-Ost-Africa, \Y, 2 (1897), 19, p. 10 

 ErFBRTH Naturgesch. mikr. SUsswass. ed. 3 (1900), p. 264 

 G. S. West in Jni. Linn. Soc, Zool. XXVIII (1901), p 

 322; and in Ann. Scott. Nat. Hist. 1905, pp. 90, 92 

 AvEBiNTZEV in Trudui S.-Peterb. Obshch. XXXVl (1906), 

 2, p. 241 ; ScHODTEDEN in Ann. Biol. Lacustre, I, 3 

 (1906), pp. 354, 355, f. 26; Landa'ceb in Pr. Ohio Acad. 

 Sci. IV, 10 (1908), p. 428; Mueeay in Ann. Scott. Nat. 

 Hist. 1907, p. 95. 



Test variable in outline, nsually broader in pro- 

 portion than in any of the preceding species, the 

 lateral border, all round, from a short distance above 

 the neck, expanded into a keel, ivhich, in most ex- 

 amples, from a broadish base thins off to a sharp edge. 

 The surface covered with scales of varying pattern, 

 mostly polygonal, and not very distinctly marked. 

 Plasma and pseudopodia similar to those of N. colla,riv, 

 Avith the nucleus normally situated. 



Dimensions variable : length 140-180 /a ; breadth 

 110-130 /A. 



Amongst Sphagnum, mostly in sub -alpine bogs; 

 not common in lowland districts. Dunham, Cheshire ; 

 Tan-y-Bwlch and Llyn Idwal, Carnarvonshire ; near 

 Towyn, Merionethshire. Glyder Fach, N. Wales (6?. S. 

 West). Moel Siabod and above Dolgam, Capel Curig, 

 N. Wales ; and Calary Bog, Co. Wicklow, Ireland 

 {J. Hnphwson). In the Highlands of Scotland as at 

 Aberfoyle in Perthshire (l^'^. Evaiix). 



Archer first reported this species from Ireland, in 

 1866, and described it in the ' Proceedings of the 

 Dublin Microscopical Club ' under the name of Difflucjia 

 cdriiuitii. Its chief feature is the peculiar winged or 

 carinate test, which in most of the forms observed is 

 seen to be a thickening of the shell-margin, suddenly 

 tapering to a sharp and in nearly all instances irre- 

 gular edge. In one form, however, which we have 

 found in great abundance on the margin of Llyn Idwal, 

 the carina has not a thickened base, but springs direct 



