34 BRITISH FRESHWATER RHIZOPODA. 
Test spheroidal in form, flattened on the ventral 
side, of a dark-grey colour with black markings; the 
outer envelope formed of small globular masses of 
organic matter mixed with silicious particles ; the inner 
membrane extremely fine ; aperture normally circular 
but capable of assuming various forms or becoming 
linear; plasma clear, colourless, granular, containing 
food-particles, starch-grains, granules of excretion, 
and occasionally a few rectangular crystals; nuclei 
small, about 100 in number, each containing’a single 
nucleole; several contractile vesicles usually present; 
pseudopodia conical, wide at the base with pointed 
extremities, one or two in number, rarely displayed. 
Diameter 75-130 pw, usually about 100 p. Nuclei 
3-5 pw in diameter. 
Habitat.—Mosses, dry and submerged. 
Iretanp.—Achill Island, Mayo (Penard). 
In submerged mosses a large form is found about. 
190-200 w in diameter, occasionally attaining to 400 p. 
1. Centropyxis aculeata var. discoides Penard. 
(Plate LXI, figs. 1 and 2.) 
Centropyxis aculeuta var. discoides 
PrnarD Faune Rhiz. Léman (1902), pp. 305-306, 7 figs.; Sarcodinés 
in Cat. Invert. Suisse (1205), p. 59. 
Dapay in Zool. Jahrb., Syst. XXV (1907), 2, p. 249. é 
Waixss in Jrn. Linn. Soc., Zool. XXXII (1912), pp. 123,128; (1913), 
p. 212. 
Test circular, discoid, larger and more compressed 
than in the type, either brown and chitinous or grey 
and covered with silicious grains and plates, with or 
without spies, which if present are few in number; 
aperture less eccentric than in the type; nucleus 
single, large, granular; plasma and pseudopodia as in 
the type. 
Diameter 150-300 «4; thickness about one-quarter 
the diameter; aperture about one-third the diameter: 
Habitat.—Aquatic vegetation. 
