NEBELA BIGIBBOSA. 57 
Three other species of Nebela, viz. N. martiali, 
N. certesi, and N. muwrrayi, are characterized by the 
two pairs of orifices in depressions in the sides of the 
tests and the tubes connecting each pair. The two 
last-mentioned species have been recorded from the 
Southern Hemisphere only; N. bigibbosa from the 
Northern Hemisphere only, where it usually occurs in 
elevated situations. 
2. Nebela griseola Penard. 
(Plate LXI, figs. 14-16.) 
Nebela griseola 
PENARD in Brit. Antarct. Expéd. I, Biol., 6 (1911), pp. 244-245, 
pl. xxiii, f. 8. 
Walttes & PENARD in Proc. R. Irish Acad. XXXI, txv (1911), pp. 9, 
18, 47-48, pl. v, £. 25 a-g. 
WAILEs in Jrn. Linn. Soc., Zool. XXXII (1912), pp. 125, 188. 
Test small, pyriform, slightly compressed, com- 
posed of variously-shaped plates and silicious grains ; 
aperture usually circular and bordered by a prominent 
collar, semicircular in section; plasma clear, colour- 
less, containing starch-grains and food-particles, also 
occasionally reserve materials; nucleus small, placed 
centrally, containing numerous small nucleoles; one 
or two contractile vesicles usually present. 
Length 80-87 w; breadth 52-60 p; thickness 45- 
55 w; aperture 18-23 mw; collar 27-32 pw in diameter ; 
nucleus 12 » dia. 
Habitat-—Sphagnum and mosses. 
Irutanp.—Achill Island and Clare Island, Mayo. 
The resemblance to N. tenella is somewhat close, 
but this species is distinguished by the slighter com- 
pression of its test, larger aperture, and (usually) 
larger size. The ratio of the transverse axes in 
N. tenella is from 4:3 to 2:1, in N. griseola it is 5:4. 
The only other species of Nebela with a similar collar 
around the aperture is N. cratera Wailes, in which 
the test is not compressed and is 120-140 p in length. 
