CERITHIUM. 195 



noted a fine almost transparent triangular membrane laid 

 on the pedal disk, which accords with Loven^s account. 

 The sides of the foot are speckled, striped or clouded with 

 dusky brown. The striae of the brown horny operculum 

 are spirally subcircular with four volutions. 



This species is found very abundantly in many localities, 

 chiefly on the west and south. It ranges all along the 

 British Channel on both sides, around the Irish coast, and 

 the western coast of England and Scotland, abounding in 

 many places in the Hebrides. Rare in the central part of 

 the Irish Sea (E. F.) It occurs at low-water-mark ; 

 very abundant, living among Zostera in the Laminarian 

 zone, and we have dredged dead specimens as deep as 

 twenty fathoms on the coast of Cornwall. The recorded 

 east coast localities seem to be due to its transportation in 

 ballast. It ranges all along the shores of Europe, from 

 Norway to the Mediterranean, though apparently of com- 

 paratively recent origin within our area. 



0. ADVERsuM, Montagu. 

 Sinistral : whorls with two or three rows of granules on each. 



Plate XCI. fig. 5, 6. 



Murex adversus, Mont. Test. Brit. p. 271 ; Suppl. p. 115. — Maton and Rack. 



Trans. Linn. Soc. vol. viii. p. 151. — Turt. Conch. Diction. 



p. 97. — DiLLW. Recent Shells, vol. ii. p. 758. — Wood, 



Index Testae, pi. 28, f. 167. 

 Turbo reticulatus, DoNOV. Brit. Shells, vol. v. pi. 159. 

 Terehra perversa, Fleming, Brit. Anim. p. 347. 



Triphoris adversus, Thompson, Report Brit. Assoc. 1843, p. 257 (no descrip- 

 tion). 

 Cerithium adversum, Brit. Marine Conch, p. 194. — Searles Wood, Crag 

 Mollusc, p. 72, pi. 8, f. 8 (fossil). 



This interesting sinistral species appears to have been 

 confounded by foreigners with the perversum of the Medi- 



