116 BRITISH FRESHWATER RHIZOPODA. 
Test a plain membranous structure encrusted in 
most cases with a variable amount of extraneous 
matter (sand-grains, diatom frustules, etc.) ; in others 
semi-transparent, chitinoid, with few sand-grains; 
multiform, mostly round in transverse or dorsal view ; 
rarely compressed. 18. Difflugia. 
Test similar to the preceding, more frequently com- 
pressed, with a constricted neck, and an internal 
transverse loop, or bridge, dividing the neck at the 
point of constriction. 19. Pontigulasia. 
Test membranous, transparent, smooth; protoplasm 
granular; pseudopodia one or more, central, digitate, 
mobile, with a terminal apiculus; and usually two 
others (one on each side) issuing laterally, which are 
thin, rigid, and tapering. 20. Difflugiella. 
Test unsymmetrical, usually forming a semi-spiral, 
with vermiform or irregular surface-markings, semi- 
transparent or opaque; pseudopodia digitate. 
21. Lecquereusia. 
Test transparent, chitinoid (rarely siliceous) sym- 
metrical, compressed in transverse section, and con- 
structed of minute circular, oval, or angular plates. 
22. Nebelu. 
Test homogeneous, transparent, plain or pitted with 
circular, polygonal, or irregular depressions, com- 
pressed transversely. 23. Hyalosphenia. 
Test chitinous, transparent or semi-opaque, with a 
faint irregularly - tesselated surfacing; compressed 
transversely ; the crown covered with a variable 
number of angular sand-grains, or spined; the mouth 
convex. 24, Heleopera. 
Test hyaline, compressed or sub-orbicular, composed 
of rectangular ‘plates disposed with more or less regu- 
larity, transversely or in oblique series. 25. Quadr ula. 
Test homogeneous, thin, transparent, flexible; 
pseudopodia lobate or digitate. 26. Cochliopodium. 
Test homogeneous, transparent, unsymmetrical ; 
nucleus single; pseudopodium single, broadly lobate or 
cordate. 27. Leptochlamys. 
