Dictionary of Ichthyology  

crucifix fish = Ariopsis felis (hardhead sea catfish, Ariidae) head skeleton sold as having attributes of the crucifixion of Jesus Christ. The arrangement of bones on the ventral surface of the head resemble a crucified person, a section looks like the shield of a Roman soldier, another section looks like a Roman sword and, when shaken, a sound like dice being cast is heard, reminiscent of Roman soldiers gambling for Christ's garments. The sound is presumably loose otoliths.

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