Amoeba (with Lithamoeba, Ouramoeba, and Endamoeba); Deinamoeba s. Chaetoproteus, covered by minute spicule-like processes; Hyalodiscus, no pseudopodia, but the disc flows onwards without change of shape; Plakopus, with membranous expansions united together, so as to include spaces, sometimes resembling Hyalodiscus1; Dactylosphaerium with rounded body, digitiform pseudopodia, and green or yellow bodies; ?Podostoma, resembles Dactylosphaerium, but has two vibratile pseudopodia produced temporarily for the inception of food; Pelomyxa (=Peiobius), pseudopodia broad, and wave-like, non-contractile vacuoles, and nuclei numerous, gorged more or less with mud, sand, food; Amphizonella, a gelatinous envelope pierced by the digitiform pseudopodia, inert; Zonomyxa, an elastic chitinoid investment, pseudopodia more or less branched, minute violet vacuoles, many slowly (?) contractile vacuoles and nuclei; Trichosphaerium (= Pachymyxa), a, coat of vertical rods implanted in a membrane, with gaps for the long cylindrical pseudopodia, multinucleate, marine.

2. Testacea s. Lepamoebae: a test either chitinoid and then flexible or rigid, in some incrusted with foreign bodies, or composed of chitinoid or siliceous plates cemented together or borne by a chitinoid membrane.

(i) With digitiform, sometimes slightly branched pseudopodia (=Arcellina, Biitschli).

Cochliopodium, a flexible cup-shaped chitinoid test, closely adherent to body; Arcella, a semi-globular, rigid, complex test (p. 898), dark-brown, with aperture limited by a horizontal flange or rim, ? young forms Pyxidicula and Pseudochlamys; Centropyxis (=Echinopyxis), test chitinoid, but aperture and fundus excentric in opposite directions, smooth or spinose, dark-coloured; Hyalosphenia, test ovoid or pyriform, compressed, chitinoid, structureless, colourless or yellowish; Quadrula, test pyriform, compressed, colourless, composed of squarish chitinoid (? siliceous) plates in transverse rows; Nebela, test pyriform, compressed, with or without appendages, typically composed of a chitinoid membrane with large and small oval or rod-like siliceous plates, sometimes intermixed; Heleopera, test ovoid, compressed, chitinoid with a reticulation of dotted lines; Difflugia, test of variable shape, globular to elliptical, often provided with processes, commonly compressed, aperture terminal or sub-terminal, composed of very various foreign bodies cemented together, - such as sand-grains, diatoms, frustules, or of a chitinoid membrane with scattered foreign bodies, or oval and rod-like bodies (as in JVebela); Lecquereusia= Difflugia spiralis, retort-shaped, with internal septum (p. 898); Petalopus, ? a test, pseudopodia ending in plate-like expansions; Arcellina, test chitinoid, with a produced aperture and pores opening each on the summit of a tubercle, (?) globular, ovate, as large as a hemp-seed, marine.

1 Plakopus and Hyalodiscus are supposed by Leidy to be identical; so too by Mereschkowski (A. M. A. xvi. pp. 194-5). Zopf believes them to be the same as Klein's Vampyrella pedata, a Proteomyxan.

(ii) With filose pseudopodia, sometimes branched, rarely anastomosing (= Eugly-phina, Biitschli).

(a) A single aperture: Pamphagus (=Plagiophrys, Lecythium, Phonergates?), test spheroidal or ovate and compressed, chitinoid, flexible, colourless, adapted to the body; Pseudo-difflugia ( = Pleurophrys ?), test thin, chitinoid, with a variable proportion of fine sand, etc.; Platoum (= Troglodytes, Chlamydophrys), test chitinoid, vasiform, elliptical or round in section, somewhat flexible, freshwater, damp earth, and putrifying substances; Plectophrys, like Platoum, but test fibrous; Cyphoderia, test retort-shaped, chitinoid, with minute oval plates; Campascus, similar to Cyphoderia, but incrusted with fine sand and two basal horn-like processes; Euglypha, test composed of oval or hexagonal siliceous plates disposed in longitudinal rows, with or without minute spines, ovoid, sometimes compressed; Placocista, test oval, hyaline, colourless, composed of overlapping oval plates, compressed, edges and base beset with moveable spines; Assulina, test compressed, oval or spherical, composed of oval or hexagonal plates, brown, aperture transversely elliptical, with ragged edges; Trinema, test hyaline, pouch-like, with oblique longitudinal axis, and sub-terminal beaded aperture, homogeneous, or composed of oval plates, with frequently beaded borders; Sphenoderia, test globular or oval, sometimes slightly compressed, with a short broad neck, composed of overlapping oval, or large hexagonal plates.

(b) With two apertures, i. e. amphistomatous: Diplophrys, globular or fusiform, test, if present, very delicate, sometimes with foreign bodies, one or more yellow or red oil-globules, sometimes colonial, freshwater, and in dung; Ditrema, test hyaline, yellowish, thick and rigid, edges of apertures somewhat inflected; Am-phitrema, test oval, incrusted with foreign bodies.

Biitschli, Bronn's Klass. und Ordnungen des Thierreichs, i. 'Protozoa' (under Rhizopoda), pp. 3-229; Leidy, 'Freshwater Rhizopoda of North America,' U. S. Geological Survey of the Territories, Washington, xii. 1879, pp. 23-232; Summaries, by Archer, in Q. J. M. xvii. 18771.