38 BRITISH FRESHWATER RHIZOPODA. 
Test of medium size, pyriform, not compressed, 
yellowish in colour, formed of a flexible chitinous 
membrane encrusted with foreign particles and diatom- 
frustules ; aperture circular, usually bordered by an 
incurved crenulate margin ; plasma partially filling the 
test, colourless but containing numerous granules of a 
brick-red colour; nucleus single, containing a single 
nucleole ; a single contractile vesicle usually present ; 
pseudopodia few, not long, digitate, simple or forked. 
Length 66-105 «4; diameter 42-70 w; aperture 16- 
30 p. 
Habitat.— Aquatic vegetation. 
Eneianp.—Isle of Man; Cumberland; Westmor- 
land! and Lancashire (Brown); N. & W. Yorkshire ; 
Sheffield District (Brown) ; Derbyshire (Brown) ; Isle 
of Wight; Devonshire; Cornwall. 
Watus.—North Wales. 
Scoti.anp. — Kireudbrightshire and Wigtonshire 
(Brown). 
IrutaAND.—Mayo and the islands off Clew Bay; 
Inishbofin, Galway; Limerick ; Kerry. 
The animal is very frequently found encysted in 
a spherical form; when it is active the plasma is 
attached to the fundus of the test by several epipodes 
by means of which it can, when alarmed, retreat 
rapidly into its test. The pseudopodia are usually one 
or two in number and the circulation of the plasma. 
carries many of the red globules for some distance 
into them. 
The test even when empty is easily recognized, and 
the internal crenulation of the aperture is usually well 
defined and quite characteristic; the neck is occasion- 
ally slightly constricted. 
In localities where it occurs it is usually abundant ; 
it is found on the Continent of Europe and in North 
America. 
