104 LITTORINIDiE. 



altogether coincides fairly with the characteristics of the 

 costaia of Desmarest and Philippi. This last writer 

 previous to the publication of the second volume of his 

 " Enumeratio Molluscorum Sicilian" sent us examples as 

 the ohlonga of his work ; hut his diagnosis of that shell 

 induces the supposition, that they belong rather to the 

 similis which he subsequently distinguished from oMonr/a. 



The shell is of an oblong-conic shape, is moderately 

 strong, not particularly lustrous, only slightly translucent, 

 and of a squalid white, more usually with the intervals of 

 the costse of a fulvous brown. The larger volutions are 

 adorned with about eight to ten longitudinal ribs, which 

 are thick, blunt, rather distant, and strongly elevated. 

 They extend from suture to suture on the penult and pre- 

 ceding turn, but only reach two-thirds down the body, from 

 the dorsal half of which, indeed, they are frequently en- 

 tirely absent. Their intervals are marked with more or 

 less perceptible spiral wrinkles, that are at times changed 

 into flat costellar lines, with obliquely longitudinal striula 

 between them ; hence, worn individuals are apt to appear 

 encircled with impressed dots. Of the eight slowly in- 

 creasing volutions the first four or smaller whorls are 

 almost always smooth. The body is scarcely broader than 

 the preceding turn, and only occupies from two-fifths to 

 three-sevenths of the total length ; its surface is rounded, 

 and its basal declination is convex and gradual. The 

 penult whorl is more or less tumid ; the apical turns more 

 or less flattened ; the apex itself is small, yet not very 

 acute. The suture is fine, but distinct. The mouth, 

 which occupies two-fifths of the total length, is moderately 

 projecting, rather obliquely oval or rounded oval, scarcelj'' 

 at all contracted above, and broadly or moderately rounded 

 below. The peristome is continuous, and of a lilac colour. 



