RISSOA. Ill 



spiral stritc (as in the allied ventricosa), is particularly 

 marked upon the penult volution, which, curiously enough, 

 projects oftentimes at the suture heyoud the edge of the 

 final whorl. The degree of ohliquity and projection in 

 the mouth varies in different individuals. Live specimens 

 are covered with a tawny epidermis. 



We do not feel disposed to augment the number of our 

 British Bissott by the admission as a species of R. venusta 

 (Philippi, Moll. SiciL vol. ii. p. 124, pi. 23, f. 4), of which 

 shell Mr. Barlee has taken a few examples at Weymouth, 

 (PI. LXXVI. f. 5.) that perfectly coincide with typical 

 specimens presented to us by the author of the species. 

 They are not unlike the ordinary ribbed form, but are of 

 a waxen-yellow tint, have their folds more remote, less 

 spread, and, for the most part, somewhat swollen both 

 above and below. The aperture is smaller and less ex- 

 panded than usual, and both body and spire are somewhat 

 shortened.* 



Fair-sized specimens measure about two-fifths of an inch 

 in length, and are about the seventh of an inch at the 

 broadest part. These proportions are very variable ; the 

 general rule being, however, that the more solid the ex- 

 amples, the more abbreviated is their shape, and vice versa. 

 Mr. Barlee has dredged some remarkably thin and smooth 

 individuals, (PI. LXXXI. f. 3.) which are actually tur- 

 reted, their length being a quarter of an inch, their breadth 

 only a single line. In these individuals (which remind one 



* The N. data of Philippi (Moll. Sicil. vol. ii. p. 124, pi. 23, f. 3) is also most 

 closely allied to the British species. So too we suspect is the gi-ossu of Michniid 

 (Esp. de Ris. p. 70, f. 21, 22), which is ascribed to England by both that author 

 and Deshayes (Lam. Anim. s. Vert. vol. viii. p. 472). The plicatula of Risso 

 (Eur. Mer. vol. iv. p. 143, f. 134) has somewhat the look of it likewise, and 

 Recluz's description of R, Souleyetana (Rev. Zool. Cuv. 1843, p. 5) agrees fairly 

 enough with this shell, except that he allows it but six volutions. 



