64 
H ELIX. SNAIL-SHEL L. 
are not disposed in a regular radiate manner, with the per¬ 
foration rather large, but not exhibiting the internal volu¬ 
tions : spires six, rounded and Well defined, crossed with 
regular close-set fine rather oblique raised lines ; the larger 
volution rounded at the margin and without the faint keel¬ 
like appearance: aperture large roundish crescent-shaped, 
the margin thin and not reflected over the perforation: 
diameter not a quarter of an inch. 
This species, sufficiently distinguished from H. radiata, 
in being quite flat on both sides, and in not having the 
slightest keel-like appearance on the margin of the outer 
volution, was found by the author in the woods near Brecon. 
Mr. Dillwyn thinks that our former species, H. radiata, is 
the I I. rotundata of Gmelin and Muller, observing that it 
is different from H. radiata, which latter species however 
he has not described, v. v. 
22. Helix umbilicata. Open Snail-shell. 
'Montagu , pi. 13. f. 2— Dorset Cat. pi. 19. f. 24. 
Shell raised‘and obtuse on the upper side, a little con¬ 
vex at the base, semitransparent, dark horn-color orchoeo; 
late brown, finely striate across, 'with a large and deep per¬ 
foration: spires five, much rounded and deeply divided by 
the line of separation; aperture roundish crescent-shaped, 
not reflected over the perforation : diameter the tenth of an 
inch. 
It differs from the young of H. radiata, in being much 
more convex, of an uniform dark chocolate brown color, 
and in not having the least trace of the subcarinated edge 
on the margin of the body volution. 
Under loose stones on the tops of walls and the loftiest 
buildings, and the crevices of high rocks, in various parts 
of England and Ireland, v.v. 
23. Helix trochiformis. Top-shaped Snail-shell. 
Montagu, pl.-ll. f. 9 
Shell produced at top, thin, transparent, smooth,glossy, 
horn-color with sometimes a rufous tinge, with a very 
small perforation which is hardly distinguishable in young 
shells : spires six, rounded and deeply divided by the line 
of separation: aperture compressed, somewhat crescent- 
shaped, 
