CEKTROPYXIS ACULEATA. 35 



ENGLAND. Isle of Man ; Westmorland ! (Brown) ; 

 N. Yorkshire; Derbyshire (Broini) ; Bedfordshire. 



WALES. North Wales. 



SCOTLAND. Outer Hebrides ; Dumfries. 



IRELAND. Donegal ; Clare Island and Mainland, 

 Mayo ; Kerry. 



The brown chitinous tests with 2 to 4 spines are 

 perhaps less common in Britain than the grey silicious 

 ones ; the latter are very rarely provided with spines. 

 In Gormire Lake, Yorks, these are numerous, whilst in 

 the sphagnum swamp at Pilmoor, Yorks, the brown 

 tests are found. The spines when present ure never 

 placed far apart, being distributed over one-third or 

 less of the periphery. 



Living animals are very scarce and active ones are 

 hardly ever seen. 



2. Centropyxis arcelloides Penard. 

 (Plate LXI, figs. 3 and 4.) 



Centropijxis arcelloides 

 PENARD Faune Rhiz. Leman (1902), pp. 309-310. 4 figs. ; Sarcodines 



in Cat. Invert. Suisse (1905), p. 60. 

 WAILES & PENARD in Proc. H. Irish Acad. XXXI, LXV (1911), 



pp. 9. lo. 

 WAILES in Jrn. Linn. Soc., Zool. XXXII (1912), p. 156; (1913), 



p. 212. 

 EDMONDSON in Ward & Whittle's Fresh-water Biology (1918),p. 221, 



f . 286. 



Test of medium size, usually brown in colour, 

 hemispherical with rounded basal angle, composed of 

 a chitinous membrane covered with small silicious 

 plates; aperture large, placed centrally in the base, 

 slightly invaginated ; plasma grey, granular ; nucleus 

 large, spherical, containing numerous minute nucleoles ; 

 numerous vacuoles usually present ; pseudopodia not 

 observed. 



Diameter 80-110 /A; height about three-fifths the 

 diameter ; aperture about half the diameter. 



Habitat. Mosses and sphagnum. 



3* 



