CENTEOPYXIS ACULEATA. 



135 



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. 



FIG. 26. Centropyxis aculeata var. spinosa. a, a well-developed form ; 

 b, an example showing variation ; c, lateral view of this form (in 

 outline). From Dimham Marsh, Cheshire, x 260. 



Dimensions: Diameter in face view 120-1 40 /A; 

 greatest width in side view 30-40 /x. 



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 



