. The British freshwater Rhizopoda and Heliozoa. dy or muddy pai^ticles, causingopacity; the mouth obliquely invaginated, its outermargin broadly rounded, the orifice (terminating theinverted neck) excentric and generally invisible. Inside view the outline of the test is nearly hemispher-ical, being broader at the posterior extremity. Inthis aspect it has some resemblance—helped by thesurface-markings—to some forms of Biflugia arcula,from which, however, the character of the mouth andthe inverted neck at once distinguish it. Dimensions: Diameter in face view about 100 fx.(120-135/^, Penard). I
. The British freshwater Rhizopoda and Heliozoa. dy or muddy pai^ticles, causingopacity; the mouth obliquely invaginated, its outermargin broadly rounded, the orifice (terminating theinverted neck) excentric and generally invisible. Inside view the outline of the test is nearly hemispher-ical, being broader at the posterior extremity. Inthis aspect it has some resemblance—helped by thesurface-markings—to some forms of Biflugia arcula,from which, however, the character of the mouth andthe inverted neck at once distinguish it. Dimensions: Diameter in face view about 100 fx.(120-135/^, Penard). In Sphagnnm; at Dunham and Chelford, Cheshire,and near Abergynolwyn, North Wales. 138 BRITISH FE-ESHWATER EHIZOPODA. The test of G. laevigata is not infrequently met within Sphagnum from the localities indicated, but fromits general opacity and resemblance to full-sized in-dividuals of Diffliigia arcula, is liable to be passed rounded margins of the oral orifice, and theobliquely inverted neck, are sufficiently Fig. 27.—Centropyxis Isevigata (face and lateral views). In Sphagnumfrom Dolgoch, Merionethsliire. x 260. Penard describes two other species of ,G. ddicnhila and G. arcelloides, both smaller thanthat under notice, and having more or less externalresemblance to Arcella vulgaris. They differ from in the structure of the mouth and otherfeatures. Genus Aecella (see pp. 118-121). Arcella vulgaris var. compressa var. nov. (Fig. 28.) ArcellavulgaiU- (pars) Leidy Freshw. Rhiz. N. Amer. (1879), pi. xxviii, ff. 6, artocrea Penaed Faune Rhiz. Leman (1902), p. 405, ff. (Non A. artocrea Leidy, 1879.) Test composed of thin chitinous membrane, yellowishbrown and semi-transparent, becoming darker withage, and faintly punctated. In face view discoid,irregularly oval, or sub-quadrate with rounded angles,never truly circular; with a centrally-situated, com-paratively small oval mouth. In side view the crown AECELLA VU
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