212 TROCHIDZ. 
moderate pot. The operculigerous lobe is prominent, and 
more coarsely fringed than the sole; it carries quite at the 
posterior end a circular, light corneous operculum with fine 
spiral strize, and has the margin serrated; from the base, at 
equal distances, three long, slender vibracula spring on each 
side from sheaths, each flanked at the base by two white 
tubercles, the one blunt, the other longer and more slender. 
These organs are in constant motion, and can be withdrawn, 
leaving only the tips visible. 
Common everywhere. 
T. umpiticatus, Mont. et Auct. 
T. umbilicatus, Brit. Moll. ii. p. 519, pl. 66. f. 1-4. 
Animal inhabiting a subdepressed, conical, strong, purple, 
obliquely lineated shell of 5-6 flattish volutions. Mantle 
plain and even. Head a short muzzle, transversely striated 
with dark cloud-coloured lines, having two very anterior, 
distinctly separated, small dark lappets at the mner angles of 
the tentacula, each fringed with about six short white cilia. 
The head-disk is large, subcireular, white, crenated at the 
margin, and puckered, having within the usual buccal appa- 
ratus. The tentacula are long, round, conically tapering to a 
fine point, yellowish-white, with dark, dull, purplish equi- 
distant rings; the eyes are on distinct short pedicles. The 
foot is rounded at both ends, oval, broad, dingy yellow be- 
neath, closely brindled above with dark stripes, margined 
with fine close fymge, with a medial longitudinal line extend- 
ing to about half the length of the sole. The neck-lappets 
are large; the columellar one is frmged; the other is plain, 
though sinuated; both are yellow, mixed with greenish-flake 
blotches. The operculigerous lobe has the same colours as 
the upper part of the foot, clothed with a dirty-white and 
yellow fringe of variable length, and has on each side three 
vibracula of the same character as the tentacula; they issue 
from white tubercular sheaths ; and it carries near the posterior 
end the usual orbicular, multispiral, corneous operculum. 
Littoral, and common on all coasts. 
