CERITHIUM. 195 



noted a fiue almost transparent triangnlar membrane laid 

 on the pedal disk, vvliich accords with Loven's acconnt. 

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

 dusky brown. The stria) 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. 

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



Plate XCI. fig. 5, 6. 



Murex advcrsus, 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. 1G7. 

 Turbo retictilatus, Donov. Brit. Shells, vol. v. pi. 159. 

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



Triphons advcrsus, Thompson, Report Brit. Assoc. 1843, p. 257 (no descrip- 

 tion). 

 CerilMum adverswm, Brit. Marine Conch, p. 194. — Searles Wood, Crag 

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



This interesting sinistral species appears to have been 

 confounded by foreigners with the perversum of the Medi- 



