FRESHWATER RHIZOPODS AND HELIOZOA. 315 
15. ArncentLa mirRata, Leidy, in Proc. Acad. Nat. Sct. Philad. 
1876, p. 56; Freshw. Rhiz. N. Amer. 1879, p. 175, t. xxix. 
A rare species which I have only obtained in abundance from 
the two following localities :—Cocket Moss, near Giggleswick, 
W. Yorkshire, amongst Sphagnum and Utricularia minor. 
Moel Siabod, N. Wales, in Sphagnum-pools. 
Height of shell 100-145 x; diameter of shell 100-152 p. 
The mouth of the shell of this Rhizopod is inturned into the 
cavity of the shell, forming a short, broad, tube-like mouth. 
. Leidy figures the pseudopodia as arising from the body-proto- 
plasm at the inner end of this tube; but in all the living forms 
observed, a ventral column of protoplasm passed from the body- 
protoplasm into this tube, completely filling it up to the outer 
end. The pseudopodia then arose from the extreme ventral 
surface of this mass of protoplasm in the tube. 
16. ARcELLA aRvtocREa, Leidy, in Proc. Acad. Nat. Sct. 
Philad. 1876, p. 57; Freshw. Rhiz. N. Amer. 1879, p. 178, 
Rinpoux. (ft 19. 
Bog above the lakes at Capel Curig, N. Wales. 
Very large forms :—Diameter of sheil (inclusive of rim) about 
800; diameter of mouth 73 m3 height of shell about 110 u. 
Leidy gives 176 p as his greatest breadth. (Pl. 28. fig. 2.) 
Churchill, Co. Donegal, Ireland. 
Diameter of shell about 85 p. 
I was unable to find any living specimens, all the shells being 
empty. The body of the shell was faceted, as in many of the 
more angular forms of A. vulgaris. It is apparently a very rare 
species, as I have never met with it from any other localities. 
Gen. Centropyxis, Stezn. 
17. Cenrropyxis acuLEata, Stein, Sitz. bohm. Akad. Wiss. 
. 1857; Leidy, Freshw. Rhiz. N. Amer. 1879, p. 180, t. xxx. 
ff. 1-32, t. xxxii. ff. 29-37.—Arcella aculeata, Hhrenb. Abhand. 
Akad. Wiss. Berlin, 1830, p. 40; 1841, p. 368, t. mi. f. 9. 
Echinopyxis aculeata, Clap. ¢ Lachm. Litudes Infus. 1859, 
p: 447; Carter, in Ann. Mag. Nat. Hist. xii. 1864, p. 29, t.1. f. 8. 
This Rhizopod is very abundant and widely distributed, and 
the shell exhibits more variation than that of any other testa- 
ceous form. Some exceptionally iarge individuals were met with 
from near Athry Lough, W. Ireland, with a diameter of 450 p 
