288 BTJCCINID^. 



whorls are more or less regular. 5 and 6, Kent and 

 Sussex ; in a bioperculate specimen, procured by Mr. 

 Rich, one of the opercula is conical and borne on a 

 cylindrical stalk-like lobe, the other being of the usual 

 shape ; in a second specimen one operculum is longitu- 

 dinally oval with the nucleus nearly terminal (as in 

 Fusus), the fellow operculum being placed at a right 

 angle to it. Other monstrosities are found, of a less 

 marked kind. Every abnormal growth of the shell can 

 be distinguished from those of a specific or varietal sort 

 by examining the apex or nucleus ; this will be seen to 

 be regular, the malformation having subsequently taken 

 place, and being in most instances caused by some 

 injury to the outer edge of the mantle. The typical 

 form and variety striata have been recorded from every 

 recent geological formation in the northern latitudes of 

 both hemispheres, and as far back as the Coralline Crag ; 

 Palermo (Philippi) . Mr. James Smith found the mon- 

 strosity carinatum fossil at Bute, and Mr. Grainger at 

 Belfast. The geographical range of the species at the 

 present time appears to be restricted to the North At- 

 lantic, from the North Cape (Sars) and Iceland (Steen- 

 strup) to Rochelle (D'Orbigny pere and Aucapitaine) , 

 and Massachusetts (Gould) ; Gulf of Lyons, in the 

 stomach of a Trigla gurnardus (Martin) . The variety 

 Zetlandica is Scandinavian, and was mistaken by Loven 

 and others for B. Humphrey sianum ; Iceland (Torell) . 

 The monstrosity acuminatum was procured by the late 

 M. Beruardi in the north of France. American speci- 

 mens of the common sort are smaller than European ; 

 and Stimpson endeavours to show that they belong to 

 distinct species, because of " a fades difficult to de- 

 scribe/' If the supposed difference cannot be defined 

 by any words or delineation, and the only substitute 



