16 BRITISH FRESHWATER RHIZOPODA. 
Waites & Penarp in Proc. R. Irish Acad. XXXI, txv (1911), pp. 
9, 14, 21. 
Waitss in Jrn. Linn. Soe., Zool. XXXII (1912), pp. 123, 129, 155 ; 
(1913), p. 212; in Naturalist, 1913, p. 146. 
HEInIs in Mém. Soc. Neuchatel, V (1914), pp. 677, 679, 693, 696. 
Arcella microstoma 
PENARD in Mém. Soc. Genéve, XX XI (1890), p. 154, pl. v, ff. 75-77; 
in Amer. Natur. XXV (1891), pp. 1071, 1074. 
LaGeRHEIM in Geol. Féren. Stockholm Férh. XXIII (1901), p. 507. 
LEVANDER in Acta Soc. Fauna Fenn. XX, v (1901), p. 7. 
Arceila aureola 
Mace in Rend. R. Ist. Lomb. (2) X XI (1888), p. 310, pl., 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, 
iInvaginated, 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 pw, or more; height about one third 
the diameter. 
Habitat.—Mosses. Generally distributed. 
Ene.anp.—Cumberland and Westmorland (Brown) ; 
N. & W. Yorkshire (Brown); Nottinghamshire; Rut- 
landshire ; Bedfordshire ; Hertfordshire ; Oxfordshire ; 
Cornwall. 
Scortanp—Perthshire, Bass Rock, and Wigtonshire 
(Brown). 
Tretanp.—Castlebar and Clare Island, Mayo; Inish- 
bofin, Galway. 
4, Arcella polypora Penard. 
(Plate LVIII, figs. 6 and 7.) 
Arcella polypora 
PeNARD in Mém. Soc. Genéve, XXXI, i, 1 (1890), p. 156, pl. vi, ff. 
2-9; in Rev. Suisse Zool. IX (1901), p. 237; Faune Rhiz. Léman 
(1902), pp. 408-410, 2 figs. ; Sarcodinés in Cat. Invert. Suisse (1905), 
Wares in Jrn. Linn. Soc., Zool. XXXII (1912), pp. 123, 204, 210. 
Test large, pale brown in colour, discoid with acute 
