RISSOA. 121 



central zone of colouring adorns the body, whose base 

 and subsutural region are alike encircled by a pale band ; 

 of these the upper and broader one winds along the 

 top of the smaller turns, so that the shell appears alter- 

 nately striped with the lighter and darker hue. 



The shell is a little translucent, and its texture rather 

 thin or moderately strong ; the surface is glossy and quite 

 smooth, and the shape is oval-conic. There are from five 

 to six whorls, which are tolerably, but decidedly, convex, 

 rather more rounded below, and considerably narrowed 

 above, since the attenuation of the spire (whose apex is blunt, 

 and almost mammillary) is rather quick ; their longitudinal 

 increase is rather gradual ; their sutural line is simple, 

 but distinct. The body, which is rather broad in proportion 

 to its length, whose basal declination is rounded, and whose 

 anterior contraction is rather sudden, is about equal in 

 length to the spire. The mouth, in perfect individuals, 

 generally occupies from three-eighths to one half of the 

 entire length, but in w^orn ones (and such are those of most 

 cabinets) is usually so abraded as to fill only two-fifths of 

 the actual length; it is oval-orbicular, and is broadly round- 

 ed at the anterior base. The outer lip is simple, acute, ar- 

 cuated, and peculiarly prominent below ; its edge is usually 

 paler, owing, perhaps, to its greater tenuity. The pillar- 

 lip, on the contrary, frequently exhibits a deeper tone of 

 colouring ; it is not much reflected, and there is scarcely 

 any perceptible chink behind it. Specimens rarely exceed 

 the seventh part of an inch in length. 



We have a note of the animal of the unifasciated form 

 of this species, communicated by Mr. Jeffreys. It would 

 appear to resemble that of ulva in several respects. It 

 is stated to be " of a light yellowish colour with occa- 

 sional brownish streaks or blotches on the upper part and 



VOL. III. K 



