120 UNIVALVES. TURBO. 



sists in its being entirely destitute of a columella to con- 

 nect its whirls; a circumstance so opposed to the regular 

 structure of all other turbinated shells, must have, of course, 

 created considerable doubt as to its classification, and some 

 authors have even placed it among the serpulae or worm- 

 shells. 



The false wentle-trap, T. clathrus, is a very common 

 shell, and is easily distinguished from the true, by its be- 

 ing much more elongated and not umbilicated ; the whirls 

 also are more closely connected. There are three varieties 

 of this species : one is pellucid, with very thin ribs ; the other 

 has its lip produced into a beak ; and the third is spotted 

 or dotted with brown. They are found in the European 

 and Indian seas, in great abundance, from half an inch 

 to two inches in length. It is said, that the ancients ex- 

 tracted a purple dye from the animal inhabiting these shells. 



The shells of the ninth division are commonly called 

 needles or screws ; their shape is that of a well proportion- 

 ed spire, with thirty or forty whirls gradually tapering or 

 diminishing from the base to the apex, and there ending 

 in a very acute point. The shells of this form are distin- 

 guished from the similar species among the Strombi and 

 Buccina, by their having a circular or orbicular mouth. 



Of the tapering or elongated Turbines may be mention- 

 ed the T. imbricatus, T. replicatus, T. acutangulus, T. du- 

 plicatus, and T. terebra, which are the principals of the di- 

 vision. 



The T. ulvae is found adhering to the ulva lactuca. The 

 T, perversus has its whirls contrary, and dwells among 

 moss on old walls in most parts of Europe, as does also 

 the T. muscorum. Among the fresh-water species the T. 

 nautileus stands conspicuous ; it is often affixed to plants 

 in stagnant waters. 



The species from the ocean are principally from the 



