TRbCHUS. 313 



T. TUMIDUS, Mont, et Auct. 

 T. tumidus, Brit. Moll. ii. p. 513, pi. 65. f. 8, 9 ; (animal) pi. D.D. f. 2. 



Animal inhabiting a conical, subdepressed, spirally striated, 

 light brown shell of 45^ 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 teiitacula 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, pointed, 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 Trochi. 



This elegant species is abundant in the coralline zone, at 

 Exmouth. It is to be considered the type of the minuter 

 forms. 



