UNIVALVES. TURBO. 109 



epidermis, rather than a local coloring. There are said 

 to be two varieties of the real wentle-trap, one having 

 only eight whirls, and perforated; the other having 

 ten whirls, and imperforated: they also inhabit ditFerent 

 places; one, it is said, comes from Barbary, the other from 

 Coromandel. The value of these shells varies in propor- 

 tion to their degree of perfection and sizej they have been 

 sold from ten shillings to fifty pounds. 



This species possesses a striking peculiarity, which con. 

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

 nect its whirls; a circumstance so opposed to the regu- 

 lar 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 umbilicated and much more elongated; the whirls 

 also are more closely connected. There are three varie- 

 ties 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 an- 

 cients extracted a purple dye from the animal inhabiting 

 these shells. 



The shells of the fifth division are commonly called 

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

 tioned spire, with thirty or forty whirls gradually taper- 

 ing or diminishing from the base to the apex, and there 

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

 distinguished from the similar species among the Strom- 



