312 TROCHID^E. 



moderate point. 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 striae, 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 These organs are in constant motion, and can be withdrawn, 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. UMBILICATUS, Mont, et Auct. 

 T. umbilicatus, Brit. Moll. ii. p. 519, pi. 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 inner angles of 

 the tentacula, each fringed with about six short white cilia. 

 The head-disk is large, subcircular, 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 fringe, with a medial longitudinal line extend- 

 ing to about half the length of the sole. The neck-lappets 

 are large ; the columellar one is fringed ; 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. 



