RISSOA. ^/ 



wise with two lines of dark-purple or black, the upper one 

 being on the side of the back, and the lower bordering the 

 foot: pallial filament pendent: snout short, wedge-like, and 

 bilobed, tinged with muddy yellow or orange: tentacles very long 

 and slender, hairy : eyes black, on -minute yellow prominences : 

 foot narrow and extensile, slightly labiated in front, bluntly 

 pointed behind; sole depressed in the centre, from which a 

 line runs to the tail : opercular lobe expanded beyond each side 

 of the foot, and margined with deep-purple or black, forming 

 with the lines on the upper surface a dark blotch : appendage 

 very long and distinct, projecting above the tail. (Alder and 

 Clark.) 



SHELL conic-oval, moderately solid, semitransparent, highly 

 glossy, and sometimes having a prismatic lustre: sculpture, 

 usually numerous fine stria-like and curved longitudinal ribs 

 on all except the topmost whorls ; these ribs are unequally dis- 

 tributed, and occasionally are fewer and stronger on the body- 

 whorl; labial rib thick and white in adult specimens, now 

 and then forming a varix in the middle of the last whorl ; the 

 surface is also more or less distinctly impressed by delicate 

 spiral striaB, especially about the periphery ; the uppermost 

 whorls are quite smooth : colour pale yellowish-white or 

 whitish, rarely milk-white, sometimes variegated by obscure 

 spots or short streaks of reddish-brown ; tip of the spire pink : 

 spire mostly short and acute : whorls 6-7, somewhat convex, but 

 not tumid ; the last occupies about three-fifths of the spire : 

 suture well defined, although not deep : mouth roundish-oval : 

 outer lip thin, contracted at the upper corner : inner lip thick- 

 ened and slightly reflected at the base, where there is a small 

 umbilical crevice : operculum resembling that of the next 

 species, except tHat this is fawncolour. L. 0-085. B. 0-05. 



Var. 1. ventrosa. Thinner, with the whorls more swollen, 

 but having the peculiar sculpture and other characters of this 

 species. 



Var. 2. variegata. Much smaller, more conical, with an an- 

 gular periphery, smooth or having a few ribs only, with flatter 

 whorls and distinct broad tawny longitudinal streaks or rays ; 

 there is no umbilical cleft. R. variegata, v. Mohrenstern, Riss. 

 p. 28, t. ii. f. 15. 



Monstr. Slightly scalariform, the last whorl being partly 

 detached from the preceding one. 



