SeaShell News, 3-10-15, Worm Shell, Shelling, Sanibel Island.
Vermicularia knorrii has a shell that reaches a length or 20 – 80 mm. The apex of this shell is pure white and translucent, while the later whorls turn to pale brown and shows prominent spiral cords. When it grows the shell becomes loosely and irregular coiled and the whorls do not touch each other any more.
Source: Worm Shell.