CENTROPYXIS ACULEATA. 137 
Less common than the type, but not infrequently 
met with in swampy ground. Very abundant amongst 
damp moss on limestone rocks, Ingleton; also near 
Bowness, Westmoreland (G. S. West). 
This variety seems to be the Arcella ecornis of 
Khrenberg, properly removed by Leidy from that 
genus to Centropyxis as a variety of C. aculeata. Ex- 
cept for its usually smaller size it might be regarded 
as typical C. aculeata deprived of its spines. From 
Arcella it differs essentially in its test, which, as a 
rule, is heavily encrusted with sand-grains; whilst 
from C. levigata Penard, it is at once distinguished 
by the character of the orifice, which is plain and not 
invaginated. 
2. Centropyxis levigata Penard. 
(Fig. 27.) 
Centropyeis levigata Prenarp in Mém. Soc. Phys. Genéve, 
XXXI, no. 2 (1890), p. 151, t. v. ff. 42-44, 49-55, and 
Faune Rhiz. Léman (1902), p. 306, ff, and p. 666. 
Test in face view nearly circular, usually slightly 
compressed on one side, composed of chitinous material, 
and covered with irregular surface-scales and an .ad- 
mixture of fine sandy or muddy particles, causing 
opacity ; the mouth obliquely invaginated, its outer 
margin broadly rounded, the orifice (terminating the 
inverted neck) excentric and generally invisible. In 
side view the outline of the test is nearly hemispher- 
ical, being broader at the posterior extremity. In 
this aspect it has some resemblance—helped by the 
surface-markings—to some forms of Difflugia arcula, 
from which, however, the character of the mouth and 
the inverted neck at once distinguish it. 
Dimensions: Diameter in face view about 100 uw 
(120-135 p, Penard). 
In Sphagnum; at Dunham and Chelford, Cheshire, 
and near Abergynolwyn, North Wales. 
