CENTROPYXIS ACULEATA. 185 
Var. spinosa var. nov. (Plate XVI, fig. 15, and fig. 
26 in text.) 
Test purely chitinous, without adherent sand-grains, 
semi-transparent ; yellowish brown when young, turn- 
ing to a darker brown with age (like Arcella vulgaris), 
and often partially or wholly covered with diatom- 
frustules. The mouth lobate or of unequal outline, 
variable in width, the margin sometimes slightly in- 
verted. Spines variable in number and also in length, 
of the same substance as the test, and frequently 
curved. 
Fie. 26.—Centropyzis aculeata var. spinosa. u,a well-developed form ; 
b, an example showing variation; c, lateral view of this form (in 
outline). From Dunham Marsh, Cheshire. x 260. 
Dimensions: Diameter in face view 120-140 p; 
greatest width in side view 30-40 pm. 
In Sphagnum; frequent in Cheshire and North Wales. 
This variety seems to have been regarded by most 
observers as indistinguishable from the type. We 
are, however, of opinion that the structure of the test, 
its more numerous spines, and particularly the lobate 
