HELIX — EXTERNAL FEATURES. 
145 
right side from the genital orifice to the neighbourhood of the respira- 
toiy opening, the corresponding gTOOve at the left side occupying a 
similar position — these are erroneously termed the Facial Grooves by 
Pilsbry. The colouring of the body is usually blackish grey on the upper 
anterior surface, but becomes whitish with ill-defined tubercles as the 
mantle is approached ; there is also a paler area below the lateral 
groove, and the spreading sides of the foot or pleuropodia assume a 
j^ellowish aspect from the abundance of minute lime cells covering 
the tips of the tubercles in that region. 
The ventral part, of the body is formed by the foot or locomotor plane, 
a large and muscular expansion of an elongate shape, but roundetl 
in front and terminating behind, in a bluntly pointed tail ; its upper 
surface is somewhat spread out or flattened at the sides and defined 
by a I’ather iiregular longitudinal groove, wliich is connected with 
the grooves or furrows separating and forming the rugosities of tlie 
body and from which about twenty-five chief fiuTOws descend more or 
less perpendicularly to the sole at somewhat irregular intervals, the 
interspaces being filled by flattish and irregularly shaped tul)ercles. 
The mantle or pallium fits in a cap-like form upon the spirally coiled 
and protuberant visceral sac, on the back of the animal ; it is of a dark 
translucent grey colour, besprinkled with yellowish specks, probably 
lime cells, and is formed by a 
thin and transparent fold of the 
integument, which becomes 
thicker and more exclusively 
glandular at the free margin or 
collar, which contains the 
principal shell - secreting cells 
and exhibits, a colouring" corres- 
ponding somewhat to the markings of the shell ; it is fused to the neck 
of the animal and encloses anteriorly a spacious respiratory cavity, 
the roof of which is covered with an intricate plexus of blood vessels 
containing the blood undergoing oxygenation on its way to the auricle ; 
a contraetile aperture for respiratory purposes, subjacent to a distinct 
yellowish patch formed by thickly clustered lime cells, is situate on 
the right side of the body and contains posteriorly within its margins 
the outlets of the alimentary and renal organs, and also divides the 
mantle into a left or anterior lobe and a right or posterior one. The 
Fig. 305. “Schematic section of Flelix^ showing 
position of respiratory cavity, etc. b.c. body or 
visceral cavity ; c. collar of mantle ; >\c. respira- 
tory cavity (after Binney). 
K 
