Banded tulip snail

Thanks for clarifying that, Sanjay.
http://www.sms.si.edu/irlspec/Fascio_tul...
This is a shot of the true tulip found in the same area:
http://www.projectnoah.org/spottings/720...

The true tulip is often confused with its close relative, the banded tulip, Fasciolaria hunteria. The ranges and preferred habitats of these two species can overlap, and juveniles may be difficult to distinguish from one another. As they grow larger, the identifying characteristics of each species become more evident. Unlike the true tulip, the shell color of the banded tulip is usually grayish and is overlaid with 4-8 distinct and unbroken black spiral lines. Also distinguishing it from F. tulipa is the color of the foot, which is black with white spots; and the smaller size of the shell in fully grown adults, which only reaches about 8 to 10 cm.