RISSOA. 31 



subulate, white : eyes surrounded by white spaces : foot squarish 

 in front and pointed behind ; the central or contracted part of 

 the sides is dark-purple : opercular lobe of the same hue, and 

 well developed : appendage conspicuous and white. (Forbes 

 and Hanley.) 



Shell conic-oblong, with an oblique outline, varying in 

 solidity according to the nature of the habitat, semitransparent, 

 and more or less glossy : sculpture, usually strong, prominent, 

 somewhat curved or nexuous longitudinal ribs, from 15 to 18 

 of which are on the penultimate whorl ; those on the last 

 whorl extend only halfway down, and almost disappear to- 

 wards the mouth; the upper three whorls are perfectly smooth ; 

 the rest of the surface is covered with numerous extremely 

 minute and delicate transverse or spiral striae, some of which 

 on the lower part of the body-whorl are raised and form slight 

 obsolete ridges ; these striae are never punctured or cancellated 

 as in R. violacea and R. costulata ; the labial rib is remarkably 

 thick, broad and white : colour whitish, with sometimes a tinge 

 of yellow or light-brown ; the mouth is occasionally of a violet 

 hue or edged with purplish-brown ; now and then specimens 

 occur which are light-horncolour and marked with reddish- 

 brown, occasionally zigzag, streaks or blotches ; the apex of 

 dark-coloured specimens is pale-violet: spire rather short, ter- 

 minating in a sharp point : whorls 7, somewhat compressed ; 

 the last occupies about two-thirds of the spire ; this is exceed- 

 ingly large in proportion to the next, and considerably dilated : 

 suture rather slight : mouth oval, widely expanding outwards : 

 outer lip thin : inner Up very broad, reflected on the pillar and 

 over the base (in some cases to such an extent as to form an 

 umbilical chink) ; the angle incident on the junction of the two 

 lips is a right one : pillar furnished near its base with a strong 

 tooth-like projection or fold : operculum homcolour, with a very 

 small spire, and strongly striated. L. 0*3. B. 0*125. 



Var. 1. minor. Much smaller, and smooth. 



Yar. 2. venusta. More solid, with a shorter spire and stronger 

 ribs. R. venusta, -Philippi, Moll. Sic. ii. p. 124, t. xxiii. f. 4. 



Yar. 3. elata. Body light-grey, with small white specks, 

 mottled with brown in front : snout short and thick, bilobed at 

 the extremity : tentacles thread-shaped and slender, setose : 

 eyes on swellings of the tentacles at their outer base : foot 

 rounded and double-edged in front, with angular corners, 

 bluntly pointed behind ; sole of a paler hue than the rest of 

 the body, closely dappled with white, and having in the centre 



