170 POPULAR BRITISH CONCHOLOGY. 



behind, and carrying a horny, pyriform operculum, with a 

 spiral nucleus at one end. The sheUs are long, many-whorled, 

 longitudinally ribbed. But the chief point of interest about 

 them consists in the fact of the shell, in a very young state, 

 having a globular, spiral form, with the whorls in the opposite 

 direction to what they afterwards assume, when the nucleus 

 becomes turned over, as it were, and the next whorl, twist- 

 ing round, proceeds in a natural direction. This gives a 

 little twisted knob to the apex of the shell. The shells of 

 the British species may be thus cursorily enumerated : — 

 C. elegmitissima : tall, white, with simple, oblique ribs. 

 C. nifa : reddish or banded ; broader, with the interstices 



of the ribs spirally striated. 

 C. formosa : white ; the whorls turreted ; interstices of the 



ribs cross-barred. 

 C.fenestrata: white; whorls angular; ribs crossed by two 



spiral keels. 

 C. scalaris: white, short; whorls shouldered; interstices of 



ribs spirally striated. 

 C. rufescens: pale reddish or banded; ribs numerous, ob- 

 lique ; interstices finely striated. 

 C. indistincta: minute, narrow, white; ribs crowded, flex- 

 uous. 



