Dictionary of Ichthyology  

Weberian apparatus = four bones and associated tissues connecting the gas bladder to the inner ear and conveying pressure changes and sound. Usually the definition includes the first four vertebrae (two and three may be fused), a supporting unit or pars sustentaculum comprising two transverse plates projecting downwards from the fourth vertebra enclosing a circular space for the aorta and the neural complex comprising modified neural arches and spines. Found in the Cypriniformes and Siluriformes.

Carp Weberian apparatus from "A Guide to the Study of Fishes" by D. S. Jordan, 1905. Photograph by Brian W. Coad.

Canadian Museum of Nature