74 LITTORINIDiE. 



are no longer to be found, and the description is too brief 

 for recognition, we retain the specific epithet by which the 

 shell is so generally known, since Montagu has clearly 

 defined and well figured it under that appellation, whilst 

 Da Costa, although prior, has forfeited his claim, through 

 wilfully substituting a name of his own for what he thought 

 the true Linna^an one. 



Turton, Fleming, &c., have rightly omitted the ob- 

 noxious reference to the Systema Naturae. Neither 

 Michaud, nor Philippi (supposing the trochlea "'* and 

 lahiata *[* to be identical, as some assert) were aware 

 that the species had been already described. 



In general aspect this shell reminds one of the genus 

 Littorina. It has an abbreviated oval-acute form, is 

 moderately strong, particularly so for its genus, of a 

 rather dull surface, and of an uniform squalid white both 

 within and without ; dead specimens, however, are as white 

 as snow. The five volutions that compose the spire occupy 

 about three-sevenths of the dorsal length, and are divided 

 by a simple but distinct suture ; the apex, more frequently 

 blunted by attrition, is rather pointed in the more perfect 

 examples. The lower whorls are scalariform, being hori- 

 zontally flattened above, and almost perpendicularly straight 

 below. The turns of the spire rather quickly increase in 

 size, yet are rather short, for even in the penult the breadth 

 rather exceeds twice the length, whilst in the antepenult 

 the proportion is nearly as three to one. The body is mode- 

 rately attenuated below : the basal declination is convex 

 and not at all sudden. 



* R. trochlea, Mich. N. Esp. Riss. p. 16, f. .% 4. — Potiez and Mich. Gal. 



Douai, Moll. vol. i. p. 207. 

 t /?. lahiata, Phil. Moll. Sicil. vol. i. p. \ah, pi. 10, f. 7 (fossil). — Desh. Lam 

 Aiiim. s. Vert. vol. viii. p. 467. 



