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204 MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 
GENUS HELJCOSTYLA Beck. 
Susp-GENus Calocochlea Albers. 
Helicostyla pseudo-globosa (d’Orbigny). 
Helix globosa Sowerby, Min. Conch., 1818, vol. ii., p. 157, pl. 170. 
SUELL globosely-conoid, with 
a blunt apex; WHORLS six or 
seven, convex and rounded, with 
obscure irregular strize or lines of 
growth, only visible in well- 
preserved specimens. The base of 
the shell is very tumid, and ab- 
ruptly sinks into the UMBILICUS, 
imparting also an almost vertical 
slope to the columella. APERTURE 
obliquely semilunate and de- 
pressed, with reflected lip, which 
at the base entirely conceals the 
UMBILICUS at maturity. 
In the immature stages the 
shell presents a different appear- 
ance to that of the adult, the 
whorls being very convex and 
subangulate, increasing rapidly in 
size, and presenting a subquad- 
rate aperture and a small open 
umbilicus. 
Diam. 32 mill. ; alt. 50 mill. 
The measurements given for 
this species by Mr. F. E. Edwards, 
judging by the original figures of 
the shell here reproduced, do not 
represent the shell as figured, 
which show an approximately 
equal diameter and altitude of 
about 50 millimetres. 
The genus Helicostylu is 
very near anatomically to the 
most primitive Belogonous 
stock as shown in the simple 
unsplit and nearly _ sessile 
mucus glands. ‘The sub-genus 
Calocochlea, to which Mr. 
Gardner allocates this species, Fic. 263. 
is a group now inhabiting the Helicostyla pseudo-globosa (d’Orbigny). 
Phillipines, New Guinea, ete., Fic. 262 and 263.—Frontal and rear aspect of shell 
inica 5 Ae es (after Edwards). 
and he thinks our species Fic. 264 and 265.—Frontal aspect of immature shells 
might even be identical with (after Edwards). 
the recent Calocochlea harfordii, while Sandberger compares it with 
Helix (Thersites) frasert from Cape York, North Australia, but it may 
be remarked that Dr. Pilsbry suggests the possibility of its being a 
member of the /7. pomatia group. 
In the fossil state, adult shells are usually imperfect and few specimens 
are found with the shell preserved, but casts in all stages of growth are 
comparatively common and in the young state resemble those of H. occlusa, 
but the rounded base, the longer and more vertical columella, and sub- 
quadrate aperture distinguish the specimens from occlusa. 
