TROCHUS. 321 



bluntly pointed behind ; sides granulated ; margin fringed ; 

 dorsal ridge serrated; tail keeled: appendages 3 on each 

 side, filiform, with an eye-like tubercle at the hinder base of 

 every filament, besides an extra or supernumerary eye-spot in 

 front between the outer base of each tentacle and the filament 

 next to it. 



SHELL narrow at the base in proportion to the height, 

 somewhat convex on the underside, with a bluntly angulated 

 periphery, moderately solid, opaque, and slightly glossy: 

 sculpture, fine spiral ridges, of which there are six or seven on 

 each whorl except those forming the apex, and about the same 

 number encircle the base ; the space between each ridge (and 

 sometimes the ridges also) is crossed by minute close-set 

 imbricated striae, which are curved or lie obliquely in the line 

 of growth, and are occasionally finer and less distinct on the 

 last whorl : colour yellowish- white, with a row of small dark 

 reddish-brown spots on each ridge, or with longitudinal streaks 

 of that colour on the last whorl and rarely on the others ; now 

 and then may be seen a greenish or partially iridescent hue : 

 spire bluntly pointed: whorls 7, gradually enlarging, com- 

 pressed but not flattened ; those forming the apex of the spire 

 are rather convex : suture slight but distinct : mouth obliquely 

 squarish : outer lip rather thin : inner lip thick, reflected on 

 the pillar, which is angulated below, and furnished with a 

 scarcely prominent tubercle that seems to form a slight notch 

 at the base : inside silvery and iridescent, except towards the 

 margin, where it is either whitish or coloured like the outside : 

 umbilicus none in the adult, but deep in the young, and ob- 

 liquely margined by a whitish ridge : operculum having from 

 twelve to fifteen volutions, which are defined by raised lines, 

 and indistinctly striated across. L. O3. B. 0'25. 



Monstr. Scalariform ; whorls somewhat angular, and sepa- 

 rated by a deep suture. 



HABITAT: All our coasts, chiefly in the coralline zone, 

 from 7 to 95 f. ; local, but tolerably common in Guernsey 

 and the west of Scotland. A specimen of the monstrous 

 variety (which is very elegant) was dredged by Mr. 

 Waller and myself at Larne, co. Antrim ; and another, 

 less symmetrical in its irregularity, was taken by Dr. 

 Lukis in deep water at Guernsey. T. Montacuti occurs, 



p5 



