Many thanks to all who answered my question about the crucifixion "shell." It turned out to be the skull of the hard head catfish, that has a "cross" inside it. It frequently washes up on the beaches of Florida and is sold in curio shops.
Thanks again.
Roland
Roland C. Anderson, Puget Sound Biologist
The Seattle Aquarium
1483 Alaskan Way
Seattle WA 98101 USA
phone: 206-386-4359
See our website: www.seattleaquarium.org