TROCHUS. 313 
T. tumipus, Mont. et Auct. 
T. tumidus, Brit. Moll. ii. p. 513, pl. 65. f.8, 9; (animal) pl. D.D. f. 2. 
Animal inhabiting a conical, subdepressed, spirally striated, 
light brown shell of 4-54 tumid volutions. The mantle is 
lax, but ranges with the aperture. The head is a short muzzle, 
having on its anterior area two small white distinct lobes ; 
the neck-lappets are large and discordant, the pillar one being 
pale greenish-white, gently scalloped and edged with yellowish 
flake-white spots; the right or outer one is the largest, white, 
with a plain margin; the buccal disk is finely crenate at the 
terminus, with a rayed sunken area of brown lines ; the orifice 
is subcrosial, and within is a minute spinous tongue, sup- 
ported by white horny plates; the head is marked above with 
fine transverse dark lines. The tentacula are frosted-white, 
long, subulate and setose, with large eyes on distinct offsets 
at the external bases. The foot is narrowish, elongated, 
rounded anteriorly, with short, curved, free auricles, labiated, 
tapering posteally to an obtuse termination; its upper lobe 
carries at the hinder part a circular, multispiral, whitish 
corneous operculum; its margin is plain, and the surface 
sprinkled with flake-white streaks; on each side there are 
three long, white, poimted, equidistant, setose, semi-retractile 
vibracula, issuing from white tubercular sheaths. The upper 
surface of the main foot is speckled with dark blotches, and 
the margin clothed, with the exception of the anterior line, 
with a short, fine, close-set fringe; the sole is flake-white. 
The branchial plume is a minute leaf of pale drab. The 
ovarium is white, and full of ova at this season (July). 
The organ of reproduction, if it be one, which I now doubt, 
though I have figured it as such—see ‘ Annals,’ vol. viii. 
p. 44, N.S.—is visibly exserted under the right tentaculum, 
as in the other minute Trochz. 
This elegant species is abundant in the coralline zone, at 
Exmouth. It is to be considered the type of the minuter 
forms. 
