16 BRITISH FRESHWATER RH1ZOPODA. 



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



9, 14, 21. 

 WAILES in Jra. Linn. Soc., Zool. XXXII (1912), pp. 123, 129, 155 ; 



(1913), p 212 ; in Naturalist, 1913, p. 146. 



HEINIS in Mem. Soc. Neuchatel, Y (1914), pp. 677, 679, 693, 696. 

 Arcella microstoma 

 PENARD in Mem. Soc. Geneve, XXXI (1890), p. 154.pl. v, ff. 75-77; 



in Amer. Natur. XXV (1891), pp. 1071, 1074. 



LAGERHEIM in Geol. Foren. Stockholm Forh. XXIII (1901), p. 507. 

 LEVANDEK in Acta Soc. Fauna Fenn. XX, v (1901), p. 7. 

 Arcella aureola 

 MAGGI in Rend. R. 1st. Lomb. (2) XXI (1888), p. 310, pi., f. 4. 



Test brown, of medium size, discoid, the base dish- 

 shaped with a sharply-defined upper edge from within 

 which arises a low convex crown ; aperture circular, 

 invaginated, about one-fifth of the diameter of the test 

 in width, usually provided with a small external lip ; 

 plasma grey, granular ; nuclei two in number, each 

 containing a central nucleole ; contractile vesicles 

 numerous ; pseudopodia lobular with irregularly- 

 indented borders, rarely displayed. 



Diameter 60-80 /x, or more ; height about one third 

 the diameter. 



Habitat. Mosses. Generally distributed. 



ENGLAND. Cumberland and Westmorland (Brown) ; 

 N. & W. Yorkshire (Brown); Nottinghamshire; Rut- 

 landshire ; Bedfordshire ; Hertfordshire ; Oxfordshire ; 

 Cornwall. 



SCOTLAND Perthshire, Bass Rock, and Wigtonshire 

 (Brown). 



IRELAND. Castlebar and Clare Island, Mayo ; Inish- 

 bofin. Gal way. 



4. Arcella polypora Penard. 

 (Plate LVIII, figs. 6 and 7.) 



Arcella polypora 



PENARD' in Mem. Soc. Geneve, XXXI, i, n (1890), p. 156, pi. vi, ff. 

 2-9 ; in Rev. Suisse Zool. IX (1901), p. 237 ; Faune Rhiz. Leman 

 (1902), pp. 408-410, 2 figs. ; Sarcodines in Cat. Invert. Suisse (1905), 

 pp. 80-81. 



WAILES in Jrn. Linn. Soc., Zool. XXXII (1912), pp. 123, 204, 210. 



Test Targe, pale brown in colour, discoid with acute 



