. “QUADRULELLA. SYMMEPRICA.. 63 
Adintat— Sphagnum. 7 
‘NGLAND.—Goathland, N. Yorkshire. 
~ Scortanp —Loch Ness (Penard).  '" ~ 
IreLa,p.—Inishbofin, Galway. 
The typical Q. symmetrica varies considerably in 
form, the outline in broad view ranging from a some- 
what wide pyriform shape with convex sides to an 
elongated form with slightly concave sides; the var: 
uregularis resembles the latter in shape, but the sides 
are nearly or quite straight and the size is considerably 
larger. 
It is not common, and records of its occurrence are 
so far restricted to the British Isles and the United 
States of America, where Penard first found it in the 
Rocky Mountains (10,000 ft.) and where it also occurs 
in the Kastern States. 
It has been suggested that the genus Quadrula 
(Quadrulella) rightly belongs to the genus Nebela, 
and this opinion has recently received further support 
by the discovery in North and South America and in 
the Tropics of intermediate forms which have been 
recorded under the names of Nebela tropica Wailes 
and Nebela scutelluta Wailes. 
1. Heleopera sordida Penard. 
(Plate LXII, figs. 10 and 11.) 
Heleopera sordida : 
PENARD in Rev. Suisse Zool. XVIII, 4 (1910), pp. 931-932, pl. viii, 
ff. 2,3; in Brit. Antarct. Exped. I, Biol., 6 (1911), p. 236. 
WalI.es & PENARD in Proc. R. Irish Acad. XXXI, txv (1911), p. 17. 
WaliILes in Scott. Natur. 1912, p. 61; in Jrn. Linn. Soc., Zool. 
" XXXII (1912), pp. 125,143, 156; loc. cét.(1913),p.213; in Naturalist, 
1913, p. 146. 
Test small, of a yellow colour, chitinous, ovoid, 
compressed, smooth except for a few adherent particles 
on the fundus which consist of silicious and vegetable 
matter; aperture wide, in side view notched or with 
the lips closed together; plasma clear and colourless,. 
the anterior portion granular ; nucleus large, granular,, 
A 
